It seems that in 0.8.1 those have been superceded by two new directories: blocks and chainstate. There is a third directory named "database", but I dimly recall that being present in previous versions as well.

As of 3/23/13, those three directories contain about 7.76GB of data, with blocks making up 7.57GB of that total.

Is copying the blockchain to a new machine as simple as pasting one or more of these directories? Is there any reason to keep blk0001.dat, blk0002.dat and blkindex.dat?