After owning a SC430 for about a year now, I can offer my opinions on it.
Awesome car, flat out. Interior is the best of any car I've owned, ergonomics are perfect, Nav system is the 2nd best out there (the one in the Infiniti M45 is better, and the one in the Acura RL). Power is adequate, torque is very nice, soundsystem is spectacular (for a stock system) but could use a touch more bass.
Bad part about the car? Handling. I even went so far as to add a Tein CS coilover kit with EDFC electronic controller and Daizen swaybars, but it's still too soft and uncontrolled in the curves when it hits any bump. The XLR's magnetic suspension is just fantastic.
If I could fix the handling on this car, I'd keep it and add a supercharger, but I don't see any easy way to do so.
One of the best things about the car? Being able to drop the top and raise it from the remote control. It is SO nice to just click the remote and walk away while the top closes and the car locks. Awesome feature. (I added this aftermarket for $750, it doesn't come like that stock).
Wish I could have that feature on the XLR, but it's pretty much impossible as the computers won't power up without the key-fob in the car, and the doors won't lock with the key-fob in there.
Nobody beats Lexus service or the 'Lexus Experience'. For anyone in NorCal, just go over to Stevens Creek Lexus and you'll see what I mean.
You drive up to the building, a large door opens up. You drive onto the showroom floor and park on the spotless tiled floor. Head over to the snack bar and grab a coke or coffee, espresso, and a donut. They'll spend literally hours telling you everything about the car you're interested in, even if you're not ready to buy that day. There's a 'business center' with a row of computers set up so you can do your work while your car is being serviced, that is, if you choose to go in. Otherwise they'll send someone to your place of business or home to drop off a loaner car and pick yours up for service, service your car, detail it, and then drop it back off again.
Awesome. But like you guys say, it's all about the car. I only take it in for service a couple times per year, so personally I'll trade the spectacular 'Lexus Experience' for all the goodies on the XLR, especially if I can get an XLR-V for a good price. I'm totally expecting the XLR-V to completely flop, just like the XLR. Not because it's not a fantastic car, it is, but because the public just doesn't want to pay $76k for the XLR, and they sure won't want to pay $95k for the XLR-V. I certainly will though. =)