I recently changed (just over a month ago) from a SAAB 93 Aero (2.0T) with all the kit (Xenon's, electric everything, in-dash 6 CD, Cruise etc etc) to an IS250 Sport Multimedia and I must say I should never have bought the SAAB (changed to it from an IS200).
I found the SAAB fast (too fast, which is one of the reasons I got rid) and reliable but the ride was a bit harsh and it rattled like a pensioner's teeth on a cold day (the other reason for getting rid). It ate front tyres for breakfast too, what with 210bhp going through the driven and steering wheels. SAAB customer service was OK, but not as good as Lexus as you would expect.
With the IS250 I've had 1 problem (creaky seat) which was fixed without question, quickly and efficiently by Lexus Bolton. It's a joy to drive, quiet as a dead door mouse and the sound system is the best on the market IMHO. As already noted, the boot is smaller than the SAAB and the rear seats don't fold, but in all the time I had my SAAB I never filled the boot (and I have a 4 yr old aswell).
In summary ... forget SAAB ... go for the Lexus