It is highly likely that as you bike you will want to bike more and more and more, and the miles will add up as will the skill level and the bike needed to meet that skill level!
Sad, but this seems to happen a lot. Biking is a rather addicting activity for lots of folks.
So, you might want to consider buying a bike that would be appropriate if you happen to become an addict. This would likely be more of a "road style" bike, as mentioned previously, perhaps a cyclocross, or the other more "aggressive" bikes mentioned previously.
Good luck and have fun.