If anyone can come up with a valid reason why it wouldn't come to pc, i'd be surprised, this was obviously coming from the day someone had the thought "so we making a sequel to GTA3:SA?".
As for image quality, I'd only buy it if there is a damn option to turn off soft shadows. THe fuzzy image quality people mention is probably that god damned awful shadow issue thats apparent everywhere but most dramatic when driving along underneath the rail tracks as you get so many shadow edges. They are fuzzy, horrible and need to be turned off.
Hopefully PC version will get, fix to the number of different car models that drive around and not be a set of 4-5 main cars in a set all spawning based on what car you happen to be driving, IE sports cars would only spawn in normal streets if you were already in one, which was a joke. Soft shadows, draw distance options, AA option or at least forceable would all make so much difference to how it looks.
THe targetting wasn't actually that bad except when you locked on and it locked on the wrong person and you couldn't get it to switch easily, but with hopefully, smooth manual targetting and aiming with mouse it wouldn't be required anyway, praying.