Save System: Autosave at mission completion. Manual save option also available in pause menu.

Review
Pros
1. A lot to do - Even side quests are mandatory to certain extent. You need to increase your respect(XP) to unlock main missions which is earned quickly by doing activities. The city is not very big but every corner is filled with something to do and they are all unlocked right at the beginning of the game.
2. Funny at all times.

Cons
1. Poor support for Controllers - Doesn't even recognises the xbox 360 controller.
2. No option to map 'shoot button' and 'shoot while in vehicle button' to different keys, so if you want to shoot gun and race vehicle with a trigger button it's going to be a big problem. You either holster your weapon or you will be continously wasting bullets while driving. You may set them to something other than trigger but that aint comfortable either.
3. Lacks polish - Graphics are no way near it's rival GTA 4.
4. Map Troubles - Its a mess, you can buy shops and places in the game. The icon remains same whether shop is purchased or not. So you have to hover over them one by one to find unpurchased locations. A mere look at map should reveal your progress.
5. Very poor zoom level in the map.
6. No on screen directions to the set waypoint. You have to see mini-map all the time.
7. AI is dumbest I have ever seen when it comes to Rocket Launchers. They treat every weapon as same. So if anyone in your crew has RL equipped, he will fire it even if enemy is standing right next to them thus killing not just the enemy but himself and even you. Enemy AI with RL behaves in the same manner too, they usually end up blewing themselves.
8. Like many other open world games as soon as you exit the vehicle the city goes under the curfew like state. Suddenly roads become completely empty. I don't understand why they do it but it shouldn't be like this at least not outside the missions. This even happens during Insurance Fraud Activity where you are supposed to be hit by traffic cars to earn points. How will you succeed if there are no cars on the road?
9. To unlock final set of missions, you have to first finish all the stronghold missions and the main missions which are available to you. There are 3 gangs, each gang has 4 stronghold missions, which when cleared liberate the neighbourhood controlled by respective gang. So on your map there are 13 icons, 12 out of these are the rival gang symbols but 1 icon is saints symbol. What do you make out of this? A simple explanation will be that the 12 icons are rival strongholds pending to be captured by you while the other icon already belongs to saints. The fact that this neighbourhood had saints pink color and all shops were purchasable further confirmed it. I was later surprised to see that no new main missions are appearing while stats say 37 of 42 missions cleared. It was only after an hour of messing around with google that I realised that Saints stronghold icon is actually a mission itself and only once I finish it will give me further access to the game storyline.