All of my bikes except the road bike have cantilevers, by choice. In general, they have the best combination of stopping power and modulation. A lot of people refer to V-brakes as an "upgrade" but that's just because they're just more grabby. The only knock on cantis is that they can be a bit tricky to set up. V-brakes were just invented so that stockboys at Walmart or Dick's Sporting Goods can get them working.
There are a lot of good choices for cantis, depending on how much you want to spend. You have everything from inexpensive Tektro to really sweet Grand Cru Zeste or Paul Components, and many in between. I've got a few bikes with Avid Shortys which work very well and are easy to set up, but a couple of my bikes have the original Shimano brakes which also work just fine. Koolstop or Velo Orange brake pads make all the difference too.
What's wrong with the brakes that are on the bike now? What are they?