Which Firewall ?

Hi
I plan to change my Firewall. Can somebody advise me which FW should I buy.Some vendors they recommend me to purchase Checkpoint or Gauntlet FW, anybody want to share any experience with me about the product. Want i want from the FW is easy to use/install/manage/support/secure.
I did read about Microsoft Internet Security and Acceleration software, how good is it compare than any other FWs in market ?
Thank you in advance