I tested one last week.
Here are the strengths and weaknesses.
Strengths:
The new spindle front end is good.
The boot is a little larger than before, but no match for a capacious front drive Camry!
The interior has higher seats, and there is a little more head room; no match for a Camry or Commodore though.
At idle, the insulation is even more impressive than the outgoing model.
Also, cruising along, the new model is even more isolated than it's predecessor.
The power steering is now actually lighter, yet more feel.
It is a little sharper than before.
The ride has improved substantially.
The old GS was a little too soft on the springs, too soft on the dampers resulting in floatiness, and too short in travel, always bottoming out.
The new GS has such long travel, like a Commodore etc.
The new GS is a fraction firmer in the springs for greater steering sharpness.
It is also slightly better damped for less floatiness.
However, the travel is really long now, giving an impressively comfortable ride.
The body structure is also more rigid than before, with no squeaks and rattles in around the glove box and the central console like the old model.
The handling is better, but not a great deal; the 5 Series is still firmer on the springs and sharper than the GS.
The current model IS250 would simply leave the new GS behind for dead on a handling circuit.
The new GS 2.5L V6 is not actually an IS250 engine.
Now it has bags of bottom end torque!
The new GS has an impressively improved equipment list including:
Fully electric boot closing.
Much more adjustments for driver's seat.
Fully automatic parking brake, synchronised with the "P" setting on the auto tranny.
Significantly more powerful, more effortless, and cleaner hi-fi system.
Blind spot and lane change warning lights.
Clearer sat nav display.
Auto dipping hi beam.
Headup display.
Rear window sunshades.
Rear adjustment for fore/aft of front passenger seat, to improve rear chauffer driven passenger legroom.
Rear adjustment of temperature, fanspeed, and stereo system.
Overall, the greatest advancement of the new GS is the longer suspension travel benefiting the ride a great deal!!!
There is also a little more room, more bottom end torque, lighter steering with more feel and more sharpness, and heaps of equipment.
The GS now has the very best engine, ride and refinement in it's class.
Weaknesses:
However, the brake cooling intakes and the foglights are bland.
The C pillar area is bland; the old GS C pillar treatment, or the C pillar treatment on the LS would be much better.
The new GS tail is very bland, some likening it to a Hyundai Sonata; the tail is no match for the prototype which it is based on.
Constructively, the GS tail end styling should have taken off the LS, or at least the IS, or even a refinement of the old GS tail end styling!
The interior styling is complex, untidy, boring, designed for the older person aka 60+, and will age very quickly; Benz and Beamer have GS beaten solidly here!
The interior only has a little more headroom, not a great deal, and certainly no match for an E Class or 5 Series.
Disappointingly, the rear foot room is only a little bigger than before; just a touch roomier - very disappointing.
The rear leg room, and the rear hip room seems to have actually diminished!
Although the new 2.5 V6 has bags of bottom end torque, it is moderately louder, and not as smooth.
There is no longer a 6 stack disc player; rather it uses a single disc player, and relies on you to play music via your own compressed mp3 music player.
The greatest drawback of the new 2012 GS lies in the poor styling, outside and inside!
Then there's the louder engines, something that is not Lexus-like, but bearable.
Conclusion
Overall, the new GS is a mixed bag compared with the old model.
In comes the superb stiffer platform and super duper ride, with lighter power steering with more feel, and greater sharpness, and a brilliant stereo.
Out goes the slick, and timeless styling, and the insulated engines.
Where the old GS had style with fair mechanicals.
The new GS has sound mechanicals, with fair styling.
Take your pick.
Pity it couldn't combine both together.
The E Class and the 5 Series will continue to romp away with sales.
The main advantage of the E Class and 5 Series over the new GS is two fold: (1) new GS poor styling inside and out, and (2) GS's slightly smaller interior.
If the new GS had retained the old GS's quietness under acceleration, then that would be a big boon to the new GS.
However, this new GS esp with it's $84k entry price, should be able to solidly kill and outsell the Audi A6 and the Jag XF this time around.
Btw, the unconventional styling of the soon to be release Infiniti M37 coming Down Under, has no hope of competing against the new Lexus GS...