go for it :)
YOu might want to check out the "rootsradicals" yahoo groups ( I *think* you can read messages wtihout joining but I'm not sure) at
http://groups.yahoo.com/group/rootsradicals/
I have an Xtracycle but I don't tote kids on it. I've found it much easier to balance than other options. If you can, find somebody close to you with one and give it a test ride to fidn out for yourself.
I was really afraid I'd have buyer's remorse when I got mine; I'd been looking for panniers 'cause I knew I wanted to be able to carry more stuff more easily. At first glance, I emailed a friend to say that hey, I'd found something that looked neat but was fortunately too expensive to really be tempting. Then 'cause it was the dead of winter I had time to read more about it, including its history, and my b ike shop guy said he would be glad to put it together for me (and he'd heard of 'em, and this was years ago before they were popular). I laughed at the testimonials that said it would change my life since I was already pretty "car-light." Welp, it really did take me to another level ... and another after that. They're wonderful machines and they proclaim to everybody who sees them "bicycles work!"
Return to your regularly scheduled stuff, now
