I've got it. Don't bother reading the review. Just go out and buy it. It's that good.
The size of the game really is amazing. I'm currently at the second area (the countryside) and i'm completely lost. You can go off roading, jump off a mountain on a dirt bike... anything you want really. Vice City is nothing compared to SA.
You can also customise CJ. Eat too much and he will get fat. Go to the gym and build up muscle and stamina. Buy different clothes. Also the more you use weapons, the more your skill will increase, until you reach "hitman" level. Your skill with Cars, motorbikes and BMXs will also increase the more you use them.
As well as the standard GTA mini games, like taxi driver, vigilante and fireman, there are many new ones. You can steal from houses at night, play pool, basketball, enter dance competitions(and dancing car competitions), street race, upgrade your car and play other mini games on the arcade cabinets around the cities.
The aiming system has also been given a major overhaul. As well as having the normal lock on, Pressing R1 and then using the right analogue stick enters manual aiming mode. This can be done with any weapon, making it much easier to hit what/who you want. CJ can also move and roll while crouching making it the best way to approach a gunfight.
Hidden packages have been replaced with tags. You'll find rival gang graffiti tags over the city, which you can tag yourself if you have a spray can. There are about 100 of these on the first island (I think). You are also able to take territory from other gangs. You do this by recruiting gang members, and then entering the territory you want. Find an enemy gang and kill them, starting a gang war. Survive the three waves of the war and the territory is yours.
As you can probably tell, I like this game. The only problem I have found is that it sometimes suffers from pop-up but that is understandable considering the size of the areas and the lack of loading times. It was worth the wait and is well worth buying.