I'll let Frank address his Lexus experience. My own experience was with
the little "Roady" aftermarket unit from Delphi ($99 special) and with
installing it (non-integrated) in my Dodge Ram (club cab) pickup.
Off-Topic for this group, but bear with me here.

I should start by saying my truck already has a mid-priced Pioneer
aftermarket sound system in it with upgraded speakers, but no outboard
amplifier and no sub woofers (and no idiotic "monster cable").

Not wanting to tear into the dash (again) I started by using the Roady's
"FM Modulator" which provided a really quick and dirty hookup. The problem
was that the fidelity was no better that an ordinary FM station, if
anything, worse, noticeably lacking highs and lows. Major disappointment.

Next I tried the casette tape adaptor. This was a noticeable improvement
in fidelity, but still nowhere near what I was led to believe was
possible. My favorite tapes, even homemade copies still sounded much
better.

Finally, at the recommendation of Mobile-One (local car audio store) the
dash was opened up and a Pioneer interface cable kit ($30) was used to
direct-wire the Roady's audio output to the Pioneer's aux input (intended
for a multi-disk CD changer). While we had the dash apart it was also a
good opportunity to conceal all the wiring and direct wire the 12v power
lead (another adaptor required because the Roady is actually a 6-volt
unit).

The extra work getting the Roady's audio output direct-wired to the
Pioneer's aux input really paid off in spades! Fidelity is magnificent!
Not quite "CD quality" but very good. It compares absolutely equal to my
son's new 2004 Accord with factory XM. Remember, the XM unit, even for the
Lexus, is only a tuner and the signal is digital. There is no audio
processing or enhancement or "quality" issues regardless of what tuner you
buy. When it comes to satellite radio, a tuner is a tuner. Price
differentials merely get you some additional creature comforts/features,
but no better quality audio.

The Roady's antenna is approx the size of a squashed golf ball and has a
very tiny black wire running to it. We started out just laying it on the
dash as far forward as possible. That sort-of worked but there were a lot
of signal dropouts, which I deemed as significant because the Roady (all
XM receivers actually) buffer 5-10 secs of program content to literally
eliminate problems with signal flutter. Obviously the antenna needed to be
outside.

With the antenna (magnet-mount) laying on the roof right by the passenger
side door edge so that the wire could be almost totally concealed in the
windshield edge seal, reception is 100% until I pull into the garage.
Remember, this is *satellite* radio, so if the antenna cannot see either
of the two satellites and you're not in one of the major metro areas
served by terrestrial repeaters, an obscured view of the sky means no
signal.

Now then, back on topic! I have a 96 LS400 with the Levinson sound package
in it (and only 54k miles). I realize that the fully integrated Lexus XM
package is not available for my car. However, if it were and if I wanted
XM radio in my Lexus, the fully integrated factory package is the only
option I would consider. Price notwithstanding and I agree it's borderline
usury, the difference in audio quality between the various aftermarket
hookup methods make all of the non-Lexus options unacceptable. If you're
wanting to put XM radio in your Lexus, do it right or don't do it.

Finally, make sure this is something you **really** want before doing it.
I've had XM now for a little over 3 months and will have to admit that the
bloom on the rose is beginning to wilt. The glow is off the marriage.
Quality is still quite good and it's nice having instant traffic & weather
and access to CNN, MSNBC, FOX news, etc. Some of the X-rated comedy is
really funny, but it's all 3-4 minute snippets and no full length comedy
show. Music (my own personal tastes for 70's pop hits) has been a
disappointment. During my morning and afternoon commutes I find there are
very few "hits" and most content is the stuff that never made it very far
up the charts. I find myself doing a lot of channel surfing.

The sound quality is great on the music stations, better than FM and almost
CD quality. On the non music stations they use signal compression so quality
varies from good on CNN to poor on the traffic reports. The antenna is a
little box mounted on the trunk lid. It comes in black but I had mine
painted to match the car. Non metallic paint. The antenna is not a very
elegant solution. It must be outside to avoid dropouts. What's frustrating
is the car has a non functional Lexus Lnk antenna on the roof which they
cannot use.