Just as GameSpot says: extremely entertaining and varied game play that shouldn't be missed.
Bad: sub-missions (not related to story, but count toward 100% completion) are mostly repetitive and VERY frustrating at times; police AI are WAY too smart (they obviously get more relentless as stars go up, but even at star one or two they can get very annoying): coming from anywhere, running up out of nowhere, a little too numerous (one walking down every other block), etc; all the safe houses look very similar; story starts out a little slow; no game pad support; you lose weapons when you die (not just when being taken down by cops); vehicles automatically catch fire and explode once they land upside down (forces you to run away as fast as possible, gets annoying after a while); map does not show how to get to a destination, just where it is: takes some navigation and map reading skills); low quality graphics textures; gang AI are semi-retarded
Overall: GTA IV was the first GTA game I ever played. I thought it was a great game, but I heard many people arguing that SA was more fun. I decided to try this game out and I'm glad I did. SA definitely has more depth to it and offers a lot more than GTA IV does. Not that GTA IV is bad, but compared to SA, it easily shows where it lacks. GTA: SA is one game ANYONE should try, especially those who enjoyed GTA IV. There's just no describing the immersion this game offers.