shiffd: Used macs can be ridiculously cheap. The apple tax doesn't happen at the used stage. Actually on the used market I find you can get better overall specs on a mac. Also macs tend to be available used because owners (like you are one) tend to be the type with a whole bunch of money they dump into their computer toys.
Seriously I have no interest whatsoever in playing vanilla versions of about 1/2 the games I bought on GOG. I have a hard time believing this isn't true for the same games for basically everyone else.
Jarmo: While the first part is true enough, I'd like to add I also bought my mac used. Not ridiculously cheap (I could have had new mini or low end imac for the same price) but it had been upgraded with SSD and better GPU, which helps when doing video editing.
I never find out beforehand if any game I buy from gog has fan patches. But yeah, once I know I wouldn't like to play Fallout 2 without killaps patch or ToEE without Co8. But I did play both Baldurs gates as they were, because I didn't see any super interesting mods right away.
One major problem with fanmods and GOG, btw, is how fan patches swipe stuff from other games all the time. Portraits, sounds, whatever is useful. While fans can get away with it (because they don't benefit financially), gog would be selling something they don't have rights to and could get into hot water real quick.
But yeah, I think I have to agree. Gog would do well to host some "essential" mods for the games that have such.
Actually, there seems to be a requested site feature for it already.
http://www.gog.com/wishlist/site/add_fan_made_patches_to_extras Voted.