Go for it!
One thing I found is riding (more or less) every day, it seemed I had lost about all I was going to, and to lose any more, I needed to eat less, or at least, eat less fattening food. So there's no guarantee that riding X miles per day will get you to the weight you want if you don't do anything else different. (What really happens is that if you just eat when you get hungry, then when you exercise more, you'll probably eat more. So you lose weight, but maybe not as much as you'd expect.)
I also find varying opinions of how riding should be scheduled. Riding every single day is not too hard if the time and distance isn't too long. But whether it's better to ride 15 miles every day or 30 miles every other day or what, is a different matter. People that are seriously training will usually have some rest days in their schedules as well. I find that I feel the best if I have an extra-hard day's ride followed by a rest day or two.
One website that I find helpful for motivation is
http://www.bikejournal.com. It lets me track my milage for the year, and compare to other people, track average speed, etc. I'm "GlacierChaser" on the forums, there, by the way.
The bicycle is basically a labor-saving devide, and sometimes, I think people get in a mental trap when using it for exercise. It's tempting to reason "I should walk 5 miles every day, but that's too hard, so I'll bicycle 5 miles and somehow get the same benefit." But to lose weight by cycling, you need to be putting some effort into it, not just moseying around. Moseying around is better than nothing, but tearing around the neighborhood is better. Speaking of which, get a speedometer if you don't have one. The $10 or $12 ones work pretty well- do a roll-out test to calibrate them. It lets you keep track of your milage and speed for each ride better.
I find that it's easy to find excuses not to exercise. In my area, it's too hot 3/4 of the year, and the rest of the time, it's too cold, too dark, too wet, too windy, or something. And to keep on a program, you just have to get out and do it anyway. A good headlight helped me a lot. Don't be afraid to upgrade your bike as you go along, too.
I started riding 3 or 4 years ago, and have lost 50 or 60 lbs, and could probably stand to lose another 40 or so. I started off riding 10 miles a day around the local bike trails. I got into riding the charity rides, did my first Century (on a single speed cruiser), and have now started randonneuring. A couple of weeks ago, I did my longest ride to date, a 305k, or 192 miles in 15 hours. My milage goal for the year was 6,000 miles, and I got that in a couple of weeks ago, and am still going.
looks like I'm on the rowing machine...
