Ok, I'm a good ways in so I'll give some spoiler free opinions/reviews;
Cars: Love (most of) em they handle great save for the SUV's I've driven which tend to do complete 180's when i move the thumbstick slightly off center.
Motor Bikes: A bit too precise, don't really care for em in this game.
Planes: Nowhere near as finnicky as San Andreas's planes, quite smoothe when not upside down or knifing.
Helicopters: Man, what happened? Helicopters were my favorite in San Andreas but they are almost unusable in 5, if your thumb stick is even slightly off center you'll wobble uncontrollably, I don't get motion sick and the Helicopter missions in flight school almost had me ready to puke.
Boats: Meh, they do all right
Jet Ski's: Wide turns but pretty damn fun.
The Sub: Haven't got it yet, it's part of a heist that you need to put Michael through pilot school to obtain.
Michael: Ex bank robber in his 40's, pretty cool dude and obvious "Main" character, reminds me of Tommy Vercetti a bit. Hate his wife, Hate his kids want to kill them. Also has the most awesome safe house in any GTA game.
Franklin: HAAAAAAATE every one of his missions. His "homie" that he loves so much does nothing but get him into firefights and end with having to duck a wanted level. He has no personality and no one listens to him. Hate Chop (He'll disobey frequently unless you buy upgrades for him with the cell phone app)
Trevor: A highly psychotic asshole that's prone to fly off the handle and is a poet with his profanity. Love this guy, he gets a lot of fun flying missions and some mildly annoying (at times) sniper missions. It takes 4 or 5 hours to get this guy though, you have to pull off the first heist to get him.
The cops: I hate what they have done with them, used to be you could get to a pay n spray or pick up a bribe star to get rid of em, and at least in 4 if you got out of the immediate area you could loose the heat, in 5 you have to loose line of sight with the police to get away and stay out of sight for a few minutes, difficult or impossible to do with certain (usually mission specific) vehicles
Cars: This game does a pretty good job of letting you keep a car you particularly like, if it de-spawns you can go to an impound yard and pick it up for a few hundred bucks. Safe house garages don;t repair damage, you have to pay to fix em and the customizations do more than change appearance, they change performance and handling, but it's real expensive to do so.
Weapons: Good variety, but you have to either pick a weapon up or do a certain mission to unlock them, but when you get them you have a standard list of attachments you can buy, suppressors, extended mags, lights, ect. and I like that you can just buy ammo instead of having to pay full price for the gun every time you want more ammo.
The Map: Scale-wise I'd say it's about half the size of San Andreas, and it's only Los Santos and the surrounding county. LS itself is slightly larger and more complex than it was in San Andreas and, truthfully, I can't find a thing without the (very nicely upgraded) mini map and the ability to to set waypoints on the pause screen map and get outlined directions on the mini map. I wish they had just taken the map from San Andreas and just moderened-up the textures , but, I guess those extra layers count.
That's all I have for now but give me a week and I'll go into more details