Support for version on Steam?
 

I'm interested in picking up the game due to today's sale but am hesitant due to the fact that the game never seems to be updated through Steam.

Do the manual patches work properly for the Steam installation or are there issues?

AFAIK the Steam version is for all intent and purposes the same as the DVD version. Could be that in the distribution agreement, the auto patching was not included, so you'll need to manually patch it.

Just check which version it is (4.07?) and start patching from there.

Is it possible to patch the Steam version (what ever it may be) directly to 4.10 or is it necessary to apply each intermediate patch between 4.10 and the Steam version?

I'm not 100% sure on the Steam version but I assume that Steam is just like having the DVD. In that case you will need to download and apply each patch sequentially. Not as clean as the newest games but it's alright once you get going.