I've played it also. Fantastic game. It fully understands it's on a handheld so missions are mere minutes so saves can be frequent. The driving is much improved and feels very similiar to older NES RC racing type games. The on foot is a bit worse than GTA IV however, but you'll spend much more time in a car. So far I've encountered driving taxis and picking up fares in them, picking up patients in ambulances, catching criminals in cop cars, racing in sports cars, buying scratch off lottery tickets for big money prizes, and the main plot involving you helping out three different heirs to a crime lord's empire. It feels more open ended than GTA IV believe it or not.
Also the visuals are the single most impressive thing in the history of the DS. The world is practically as large as GTA IV is. The game does feel a bit more fun. I'm 6.8% through the game and I truly feel like I havent scratched the surface. I'll keep you informed, but please do get this game. It's a gem.
Edit: I forgot the best part. There's a fully working economic system around buying and selling drugs around Liberty City. It works similiar to the property buying system in Fable II. Also the game has many DS specific features like three different ways to hotwiring cars all built around the touch screen interface.
Double Edit: I forgot to mention that buying property is back. I haven't been able to afford any additional apartments but they are there to buy.
