So far I have had no problems other than those of my own making!
X2 4Gb in my Nikon D7000 (slot 1 ) connected to iPad 2 16Gb iOS 5 by direct mode. Then, when in range of my home WiFi PhotoStream sends the images from the iPad to my MacBook 2.26GHz Intel core 2 duo OSX 10.7.2 with no issues at all. This means EyeFi, the iCloud and SD card slot 2 always have a copy of the image. Belt and braces!! All ready to try the next iteration!