I am working as a valet right now and drive all these cars on a daily basis and this is, in part, what leads me to my desire for an IS250. At this point, in terms of exterior design, the IS blows the TL away. The TL had an update recently but the design is still quite similar to the initial one from the early 2000's. The G35 looks great, but all those smooth body panels sure do show off dings in the doors mighty nicely.
As far as the interior goes....every new model lexus i have driven, no matter what series, is leaps and bounds above anything lexus has put out in previous generations(and i drive older models of each brand on a daily basis as well). The TL guage cluster is pretty, but looks gimmiky pretty quickly and in the dark, the G35 guage cluster looks cheap at night, the lexus oozes quality....
I'm a design junkie and have a degree from the savannah college of art and design, one of the best art schools in the coutry. Now that we know i'm qualified to pass ULTIMATE JUDGEMENT on the cars, really, the lexus seems to be better designed and better built than the other two. Keep in mind people have gotten them at $500-$1000 below invoice as well.