You can make everythink look awesome in a video. I hope you guys remember how they fucked up the GTA IV MP, although they had the SAMP-mod as a perfect blueprint for a succesfull MP. Biggest failure were not using dedicated servers, but instead let players host the servers. Result were crashing servers because of high graphics requirements, fail bans from servers, poor available server options and so on and on... (not to forget about all the patching bullshit and Games for Windows Live and Rockstar Games Social Club)
GTA IV on pc felt like they forced a console game onto the pc with a sledgehammer. I really hope they learned their lesson...
Like Epoxi said, a good balance between IV and SA would be fine. Driving an Infernus in IV was a mess cause ALL cars were just bobbling around like a muscle car, I want to have more choices in V.
Oh and finally, let's hope for a good story and nice missions. I played IV just yesterday and already got pissed after 1 hour, because you get calls every 5 minutes ("CHEY NICO LET'S GO BOWLING NAO"), police AI sucks big time (they can't do anything but block you with 100 cars) and the mission all consisted of "Drive there and kill this, drive here and get this, drive there and bring me this".