Well I bought it. And it's running really well. High settings and 1080p. What's the deal with mods then? I want to install some, but will they adversely affect the performance of the game? GTA IV mods seem to really slow down my game. And will I get banned for using them?
I finally installed mods a few days ago, and I'm not going back! Police is much more fun thanks to Crime and Police Rebalance & Enhancement, the map view is better because of Satellite View Map and shootouts are better due to More pedestrians and traffic. There are many more, I personally can't wait for the new release of LCPD:FR, it was awesome in GTA IV.
Regarding bans, if you use mods online you might get banned, offline is safe. A very popular tool is GTAV Mod Manager which automatically sets everything to offline mode and basically safeguards you.
I'd recommending finishing the game first then using mods, there are apparently a few odd occasions where some of them interfere with missions.