I've been doing this for a few months - and it has made an amazing difference already. I've now got a bike and a toddler trailer and am starting to ride the kids to the playground every day. It's three miles - uphill on the way there.
Honestly, do it and it'll make you feel so much better!
Oh and I've lost a load of weight, don't know how much, don't own scales but enough to drop a clothes size without trying.