Do it! The GS450h was probably the fastest car I have ever owned (and I've had TVRs, Supercharged Jags and the SL500 and always have a number of fast bikes in the garage too), but it was so much more than just fast, the hybrid system on it is amazingly good, the 2 speed diff is great for acceleration and then cruising, the 6 speed CVT takes a bit of getting used to (just the way the engine sounds, totally different to a standard autobox, the revs hardly change). It had every gadget you could imagine (mine was the SE-L),
No matter what though, I only ever did 27.5MPG (measured over almost 70,000 miles of ownership), the electric range was around 3 miles, great around town and huge fun trying to get it into electric mode on the motorway (you really need to finesse the throttle).
In my ownership I claimed 2 pedestrians, a jogger and a cyclist - all of whom "didn't hear you mate" and none of whom LOOKED!
My wife hated it that the first thing she knew about my arriving home was when the front door opened - I haven't investigated why she feels she needs the advance warning!
It was comfortable (not LS comfortable, but plenty good enough) and with the hybrid in "power" mode it could take almost anything from the lights (electric motors make maximum torque from 0 revs), 0-60 in under 5 seconds is M5 territory.
And like most Lexus (Lexii?) it was faultless in 3 years and 70,000 miles of driving.
I already miss the "keyless entry/keyless go", but TBH I think I can rig that up on the LS without too many problems, I already have on my Smart Roadster and reckon the same approach will work on the LS.
The James Bond style hidden buttons on the GS were a good talking point, the heated AND cooled seats were great (I miss the cooled seats already).
Honestly they are great cars, I'll have another one someday, but after it being my "everyday workhouse" I just got bored, but I was doing over 25k miles a year and spent a LOT of time in that car. I've changed jobs now so my mileage is going to be closer to 16k now including private miles, as opposed to 25K plus the private miles, and I can spread those miles across the entire fleet (don't ask) so the LS will have a 5000 mile policy applied.
Pay the extra for the Mark Levinson audio system - it is worth every penny, and the "radar guided cruise control" is awesome, especially in the fog! And I miss my reversing camera too... so many things I miss :-) fortunately most of them I can fit to the LS with no great hardship.
The only thing really wrong with the GS was - it looks bland, ordinary.. I've had people this week come up and say "nice wheels" for the first time in 3 years..