IMO first person mode is really tough. When in first person, I kick into FPS gaming mode and expect my health the regen and such. Nope. Forgot that health is very finite in GTA5. I wish they had an option to do full health regen instead of health packs. That would make this game sooooooo much better in FPS mode. I've already beaten it on PS3, so I just want to have fun.
The aiming is kind of strange too. It doesn't have much auto aim where you just sit the cursor in the general area and shoot like in destiny. You have to be spot on with the tiny bead to hit them. You can use the left trigger snap aiming, but that is really weird in FPS mode.
Will probably get the PC version on sale after release for the mods. Health regen + >60fps will be great.