I just bought Halo 3 for $39.99 at FYE at The Gardens Mall in Palm Beach Gardens, FL. I also got a mail in rebate to get $20 back to make it $19.99. Hopefully that deal is everywhere but I have no idea if it is. If you don't have the game yet I'd say it's worth a phone call at that price...
I bought the game yesterday for 360 at Gamestop and mine freezes during the intro. Son of a bitch what a tease! So I took it back today and got a new copy and it still freezes. The only thing I can find in the forums is that (allegedly) the system loads so much data from the disc at a time...