I have owned a '98 for four years today (!). I could tell you volumes...
I posted a long laundry list of things to check over at
http://townhall.edmunds.com in the main Aurora discussion
(username=hammen2).

Another Classic Aurora site by a (now-former) owner:

http://members.fortunecity.com/zincster/

Pics of my Aurora when I first got her four years ago today:

http://www.hammen.net/car/

I would personally stay away from the '95's and '96 cars due to issues
with the shift solenoids in the tranny. This was revised halfway through
the '96 model year. The HVAC controls and rear window changed from '95
to '96.

'97 had a different suspension than '95 and '96. '98 and '99 had it
revised again. I haven't driven the other years but understand it's more
"wallowy"/less sporty.

Common failure issues:

1) Northstar rear crankshaft seals leaking - basically, there's one big
seal at the back of the motor. When this starts to leak, the engine and
tranny have to be dropped, and the engine split apart and resealed using
a redesigned gasket. An $1800 repair. This was a problem with many
Northstars through the '97 model year. Supposedly the redesigned seal
was installed starting in '98 but my early-production '98 had this
problem. I had an extended warranty which fortunately covered most of
this repair.

2) A/C compressor is a little underpowered for the car. Don't ever let
it get low on refrigerant, or the compressor will grenade. Yep, happened
to me (black car, black interior). Thank goodness for the warranty.

3) Clicking under the dash/flashing headlights. This is actually too
much grease on the multifunction (headlight/turn stalk/cruise control)
switch. Don't need to have this replaced ($275 for the part), just take
it apart and clean it out good. Instructions can be found at
http://www.automotiveforums.com in the Aurora section (Google "Aurora
Multifunction Switch" and see if you can find them).

4) Fuel Pressure Regulator will leak and need to be replaced. A simple
DIY job, should be considered part of maintenance.

5) Check the rear window seal for signs of leakage/warping/removal.

6) door controls (seat movement, heated seats, et. al.) may be erratic.
This is due to the small gauge of wire going through the wiring
harness/boot. May just need to run new wires.

7) There is supposed to be an air deflector/dam which helps cooling. The
Aurora runs a little hot - just under 200 degrees on normal days, as
much as 220-240 if sitting in traffic (no grille - air must come up from
under the engine, and if it's a hot day/you're not moving, this presents
an overheating risk). Make sure the air dam is there - it's part 2567777
if it isn't, about $21 through any GM dealer.

8) Battery is under the back seat. This helps with weight distribution
and keeping the battery lasting longer. It's a huge battery and I've
only ever found AC Delco as the replacement. Ensure that the ventilation
tubes are hooked up, as I've otherwise heard of fires due to battery
gases building up.

9) Speaking of fires, '95 through '97 Auroras had nylon fuel rails which
could develop cracks and eventually lead to fires. There was a recall
for this which had steel fuel rails installed. '98 and '99 had a
different rail which was unaffected.

10) I believe the '95's used the old green coolant. GM found that it
presented a problem with and aluminum engine and thus switched to
Dex-Cool in '96. I've heard good and bad regarding Dex-Cool but I
haven't had problems on any of my vehicles. Of course, I get the coolant
flushed every couple of years or 40k miles, whatever comes first.

I'm sure there are other things I'm forgetting... I would personally
look for a '98 or '99 as, typical GM, many of the issues from the
earlier cars are fixed in the later gen. I have the "Autobahn" package
on mine (no speed limiter, different gearing for faster acceleration)
and love it. Look for option code QQX on the RPO build sheet in the
trunk.

I've got just under 94k miles on my Aurora now (had 27k when I picked it
up). Despite having some expensive repairs (thank goodness for the
extended warranty, for which I got back more than 3x what I paid for
it), I love the car. I picked up a fire-sale 2004 GTO (Holden Monaro)
and am now using the GTO as my "summer car", storing the Aurora until
more inclement weather (with good tires, it's the best winter car I've
owned).

IMHO GM's not built anything nearly as stylish in the Aurora in the past
10 years. That's why their market share continues to suffer...

The 98 I have is outstanding as far as running, before you actually
write a check, road test it to speed and step on the brakes. If it
wobbles, etc. your rotors may be warped, seems to be a recurring
problem for some reason and expensive to fix.

Rear seal around trunk, upper section is a pain too. The engineers
were pushing the envelope for performance on that gasket, as it is
cheap compared to what it is supposed to accomplish.

Other than that, I think its a fantastic vehicle, but if you are
offered an extended warranty, don't quibble, grab it before they
change their mind. It pays for itself constantly.

Hi Zaphod Beeblebrox and Patrick t:

Thanks for your comments.

I'm still looking for is car in my area....southern Oregon.

Regards,
Al Gershen
Grants Pass, OR
aldg@webtv.net or
aldg01@gmail.com

 I've had rather good luck with my '95 Aurora (knock on wood!). 155K
body, 100K on motor. I've had it 1 year now. I bought it very
reasonably, so really can't put a boat load of cash into it.
 Great in snow. Very comfortable, roomy, interior -- giant trunk.
 Up to 30 MPG's driven carefully at ~ 55 to 65 mph. Using boost & coast
method, "scrubbing" off speed up hills. Must be very aerodynamic.
  I've heard bad reports (especially electrical) but mine has been
rather trouble free. However there are some problems I'm living with &
keeping an eye on: The "check engine light" used to come on,
intermittently, but after a little hard driving, and letting it come up
to full temp ~ 235 degrees. It hasn't come on, in months! (EGR? cleaned
out?), The climate control used to flash, occasionally, on start-up, but
this also seems to have corrected itself, (it didn't effect function,
anyway). The trans had been clunking from N to D & R, We tracked it down
to the rear motor mount ($260 -- part alone f/GM) - but now -- with no
more quick starts off the line & letting the idle settle down (a couple
extra seconds) to ~ 600 rpm, no more clunking. I realize a motor mount
failure could be dangerous so I'm keeping a close watch on it.
   One major, dangerous, problem popped up -- the 3 bolts connecting
the steering components (main shaft to rack?) were very loose according
to my mechanic at the 1ST oil change. A quick $25. fix.

 CURRENT PROBS:
  I hope it's just a small glitch, but my drivers window stopped
working recently. It's stuck fully up (a bit of good luck). When the
switch is hit, up or down, a quiet click comes from inside the top of
door.  
  The cruise control only "holds" briefly then no cruise. Vacuum leak?,
switch?, no biggie, but would be nice to have.
  SEE ADDITIONAL  POST. Any suggestions appreciated.
  Thanks Much, Dave