I'm a big fan of this game now that it is on the Greatest Hits collection. Initially, I rented it through RedOctane's unlimited rental and I think I kept it for like 3 weeks. It didn't take that long to open everything, but it had great replay value.
I wanted to buy it for a while, but given the fact that I was buying it for replay only, I couldn't part with full price with so many other new games around. I figured that sooner or later, the price would fall, or I would pick it up used. But, since this game is so popular, the price never went down, even for used. So, when they decided to put it on Greatest Hits, it made my day.
Go out and find this game! It's a real hoot. Especially at $20