I think you'll have to be the ultimate judge. I commute about that far and I have some significant grades to deal with. I think the main thing you want to consider is how much time you should have for a cushion....esp. the first few times. In other words, you don't want to say unequivocally that it's going to take X amount of time to get to work or school and then leave your residence with that exact amount of time to get there. Take into account flats or other bike issues, detours, weather problems, your physical conditioning, etc. After a few commutes you'll get a better feel for it.....and you can decide whether the sacrifice of time (and sometimes sleep) is worth the benefits. I've found looking at it as a challenge, saving gas, and helping the environment does help.....but if you don't enjoy it at least a little bit you probably won't want to keep doing it. Most of it is mental, not physical.