The two biggest issues are the host-mode USB port not being installed (due to some silicon issues with the USB chip), and some minor bugs in the silicon on the OMAP3530 that can impact NEON performance. Both issues can be worked around fairly easily, though, since the OTG port is available (as long as you have a 5v adaptor for power) and the NEON bugs have been worked around in the community code. Rev.C is probably due around November, it's not clear whether it will have updated OMAP3 silicon, though.