i just raced my second cross race ever yesterday and you should do one (or more)this year at least just to get a feel. plus you get to see all kinds of cool cross bikes. hardest 35 minutes (except for last year when i did my first race!) but i plan on doing all 4 of the urban cross series here in so cal. there were plenty of people racing mtn bikes and for your first couple times wouldn't be that bad. at least at yesterday's course there wasn't a ton of carrying the bike. the worst part was a steep uphill but it proved easier to push the bike. it's super fun and SUPER hard. come check one out and try just the men's D/firstimers group.