I also got the entire rockstart collection on steam when it was on sale. Pretty glad I did seeing how most of the GTA games can be modded quite far. Recently I've been trying to install some police mods onto GTA4 for the fun of it but either because I'm not doing it properly or the Steam version is patched too far, they only partially work. And because I'm clever, I never made backups of any of the files.
So right now I'm redownloading the entire (almost) 16gb that is GTA IV. Yay.