Hello - I'm a total newbie to biking, commuting by bike, this board, etc. Actually, I don't yet have a bike but that will change soon. I'm seriously considering a Dahon Speed TR folder. For purposes of this post, I don't think the model matters much except that it's a 20-inch tire model. Here's my thinking, please point out any problems you see or whatever.

No bike riding in 25-years. 6-foot male at 175 pounds. No back or joint problems. Reasonable shape - I walk about 30-45 minutes a day. The bike is a present to myself for losing 50-pounds this year - <begin_plug> weight watchers ...

Without vastly changing the the things I do and my hobbies, the only time I'll have for riding is if I commute. (Other than a weekly or so jaunt along a nearby bike path - paved but occassionally muddy as its borders a river.) My commute would be about 3 miles along said bike path, a bus for about 14 miles and then a 1.5 mile route along a mostly empty street. The buses here have bike racks on the front so a folder is not necessary for that reason. I know a cheaper bike would work for this still fits in the budget.

I'm thinking folder anyway because:
1) I think it's cool and this is a present to myself.
2) If the weather turns during the day, I can hitch a ride with a co-worker who lives nearby and put the bike in his trunk.
3) High-end folders seem to hold resell pretty well if I just hate this idea after trying it.
4) I don't have any big bike habits or preferences to overcome so why not start out with a more nimble, small wheeled bike. It will be more like the last bike I rode than any 26-inch or 700 c bike out there.
5) Security - No questions in my mind that I can bring my bike in wherever I decide to ride it. If I really get into biking, that may change as I ride to more places but that's a bridge too far.

What are some down sides that I should consider?

Thanks in advance for your thoughts - I've learned a lot from reading these forums.