Moving storage to the SD card really does nothing more than moving your home directory to the SD card. In the file system, there's /intsdcard and /extsdcard. /intsdcard the 3GB builtin. /extsdcard the SD card in the slot. What moving storage does is point /sdcard from /intsdcard to /extsdcard. It also copies everything to the SD card, preserving what was stored internally (which saved me from losing my notes and Adobe registration). After moving, all the internal storage does is store settings and programs. Existing 3rd party programs didn't have any issues. The program storage is NOT increased though.

Reads from the SD card are normal. Writes are stupid slow with the Library app. I'm using a class 6 SDHC card and I'm seeing 150-200KB/s writes in the Library app. Writes using anything else are normal. I copied a 54MB file from a USB flash drive to the SD card and by the time I opened the notifications to check the speed it was finished (3-5 seconds). I'd say the Library app needs some work.