I no longer have frequent need for a transmission jack but,
I tried the one that adapts a floor jack.  I found it was a
bit unstable at full height because of the rather narror
width of the jack wheels.  Any wear in the lift arms which
is usual after a few years use with a floor jack made it
almost unuseable.  The inability of the front wheels to
swivel makes it tough to guide the trans in.

I next tried the one you are looking at.  It is also a bit
wobbly because of the scissor part of the jack lift.. I also
found it hard to install the trans working alone without a
way to tilt the jack for alignment.

I ended up getting a cheap hydraulic jack that works OK for
a hundred bucks on sale at Northern.  I made a couple of
small tweaks to it and it works pretty well but not nearly a
well as some of the commercial duty jacks I have used.  The
one I have and works OK for limited use is here:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=3185

If you plan to do more than a couple a year, you need to set
your sights higher.  You might also keep in mind that many
of these tools effectively pay for themselves on the first
use.

You might also check into tool rentals in your area.  Most
places around here will rent a hydraulic trans jack.  The
cost may be much better if you plan to do an R&R in one day.

Lugnut