Good for you, that is great! 6 miles is my commute distance too, you will really like it. I am full-time commuting by bike now, although 5-for-5 weeks are rare due to my job having lots of business travel and overnight stays, etc. I don't know much about the mongoose you mention, but I will suggest fenders (if your bike will fit them, some won't), a rear rack (if your bike will fit them), and good waterproof panniers for the rear rack. If you can afford Ortlieb classic backrollers, you will love them every day you commute. Good luck, and good move... you will love the 6 mile commute.