Haven't seen much live action and what I have seen is not sound for judgement. What kind of races did you watch the Skylines participate in? Club level racing is sort of unhelpful for determining how cars will perform in professional series.
A little more info the 12 Hours of Sebring for anyone reading the thread. On Speed throughout most of the day...here are some interesting entries in addition to the dominant R8s, Vettes and GT3s in case you need some more convincing to watch it:
TVR 400
Spyker
Maserati MC12 (the enzo-dervied GT1 car)
Aston Martin's new DB9 GT1 car
TVR 400
Fully entry list and site link:
http://www.imsaracing.net/2003/event.../entrylist.pdf
and
http://www.sebringraceway.com/information.html