There are some test shots of the Nex-5 circulating around that more or less killed the hype of the system. The links I saw those pictures in, however, did not indicate whether those test shots were taken with the pre-release models or not.
One thing the NEX-5 did excel in is its ISO performance. 1080p HD video should come in handy as well but only if autofocus works well unlike the Olympus EP-1 before the firmware update.
I feel like the size difference between the NEX and other MFTs and NX10 is irrelevant. Unless it is significantly smaller (ie. pocketable), the difference in size may compromise handling. Am I the only one who finds the GF1/EP1 more attractive in terms of form factor? NEX looks funny with the small body and a (comparatively) huge lens. Different strokes for different folks, I s'pose.
No one can be a fair judge of these interchangeable lens cameras until the NEX-5 comes out and is formally tested.. There are previews and reviews available by gadget geeks but I've found too many of them biased to be reliable.
Anyway, if you already own the GF1 or EP1 or other interchangeable lens camera/MFTs, don't second guess your choice and enjoy your fine piece of photographic technology.