SSD write leveling?

It's worse than just losing a single block.  A flash erase block can include many filesystem
blocks as it's quite large - anything from 16 to 512 KB according to
http://en.wikipedia.org/wiki/Flash_memory#NAND_memories.  And in some devices with poor FTLs,
interrupting a single write can cause the whole device to fail - it's important that when the
device comes back up, the FTL checks for partially written erase blocks and marks them as bad.

Unfortunately FTLs appear to be mostly undocumented so you just have to rely on going for mid
to high end flash products from a reputable vendor, assuming you care about reliability.
Embedded flash products (e.g. CF drives) seem to have good reliability specs and may be a good
option, at some extra cost.