Although the delay in the release of GT5 is a disappointment, its not the reason I've stepped back from GT5P.
I recently got Supercar Challenge and NFS-Shift. And although SCC isn't really much cop, NFS-S isn't half bad - the physics are closer to GT5P, and I'm loving The 'ring again, now in 720p.
The update last week of GT5P online events was a letdown for me too, although I'm sure ride-on mowers on any old goat track would be worthwhile with the SAR/MNR fellas.
But primarily, its The Nurburgring on NFS-S... just a blast!
If you've not got NFS yet, I'd give it my recommendation. No, its not GT5, but its a decent filler until March arrives. A reasonable selection of cars (with Porsche, no Ferrari), and a few decent tracks including the likes of Road America, Willow Springs, Spa, Nurburgring etc.