In reply to mh554:
Depends what you're climbing.
On long mountain routes I take them, using them where I would be using a cam in a belay (I look for nuts first though), this saves any cams for the leader of the next pitch. For me it's much nicer to place a quick cam than a tricam when stressed.
They're also pretty light compared with cams and have good range. If I'm climbing below my limit in the mountains and want to go fast I'll use these as I can generally use two hands to seat them on easier ground.
They're also good for specific placements like narrow shot holes on grit or funny limestone pockets so they're not just for multipitch by any means.
What I don't like about them is how fiddly they are. Placing them above your head is tricky as they flap around. Seen someone strap a straw to them with finger tape but I cba with that. Cleaning them with a nutkey is easy, but you have to explain how to do it if someone has never done it before.
Overall IMO, they're no replacement for cams but they do come into their own in specific situations!