Ports are hit and miss, I haven't played AC4 yet on PC, (Still haven't played AC3 and its installed) but usually framelimits are easily fixed by the mod community. If you jumped over to PC hoping to just use PC to play games intended for consoles you might have been premature, because if the Steam Box is successful it might make porting more stable.
I recommend using your new PC for the ground breaking ability to play games from THE PAST! (Spooky voice). Download some good games that are either well adapted to PC or PC exclusive. If you want Battlefield, play Battlefield 2, its got a nice online community still active and is basically the same as it was the template for CoD4-BF4/CoD:G. Ports will almost always get fixed and surpass their console versions but it does take time. I rarely preorder anything that isn't a PC exclusive because I know that A) next summer/winter it will be on Steam for significantly less money, and B) the initial port is going to be full of bugs.
The big warning from me, and this is my main regret with PC gaming as well, is that some of the old games never got properly fixed, most new triple A games will get fixed but some old PS2 era ports never got proper fixes from the community so do some research before buying anything, Steam community usually has good info on how to get old games working or just google search stuff. Steam sells the original Fallout games but they don't work properly if you just let steam install them, however, if you take about 30 min to fix them, you can get them to run better than they ever did.
And make sure to look in to getting mods, especially with any Bethesda games, their base games are great on consoles but the porting is usually kinda sketchy, I think the Unofficial Oblivion Patch has over 400 fixes to the game alone, not including things that make it work better.
My only regret to PC gaming is that I can't play some exclusives, but when I get most of my video games for under 10 dollars I don't mind missing out on paying $60+ for The Last of Us.
Also if you use Steam, look up the various discount hunting steam groups, they offer great deals on games all the time, I've gotten like 5 free games this year because of them, just don't be a jerk and abuse developers being nice like people did to Blackwell.