I'll definitely buy DotA2 if its sold as a whole. If its a monthly subscription I would have to think about it first. My university blocks steam, unfortunately, but with a proxy it is easily remedied
1) Are you willing to pay 2 play? (Regardless of 1 time fee or monthly)
2) Do you know how valve steam works?
Sort of. You get to buy some extra misc stuff for the game, right?
3) Is your PC capable of running Source engine? (Or L4D quality)
My Mac is capable, hopefully.
4) Do you have Imba (Godlike) internet speed?
5) Do you even have any original games?
All my PS3 games are required to be original, unfortunately.