Why would anyone want to be on a version that the miners are not using? ... you are opening yourself up to the possible risk of ending up on a useless fork.
People end up on whichever fork is longest and the mining pools will outpower anything else, leaving you on the right fork...as long as you can accept what the mining pools put out.
If you use a 0.7 client, that'll work only until the mining pools switch to 0.8, produce another incompatible block, and leave you on the wrong fork.
If you use a 0.8 client, that'll work now
and after the switchover.
So, if you're not submitting newly-mined blocks, you should use 0.8.