I'm a fan. We've had our Chariot trailer for, from memory, about 3 1/2 years. We had a lot of fun with it. Maybe it was just me, but the kids' day seemed to start better when I dropped them at daycare on the bike, rather than in the car. It's done plenty of trips to various parks too. It has some other perks too, like the fact that I get to park on the lawn, right out the front of my eldest's kindergarten (I asked and that's where they suggested parking. No worries!). No looking for a park then walking down the street for me!
For rolling around on weekends, it's brilliant. You just pick a trailer-friendly route to the interesting place of your choice. Sorted! It works pretty well for shopping too. Two children and a week's worth of groceries is a bit ambitious, but it'll hold a fair few groceries. Commuting is a bit of a mixed bag. Probably the biggest issue is finding somwhere to park. If there's somewhere suitable (like the front lawn of the kindy :) it can work well. If not, it can be a bit of a drag. Going on to work afterwards towing a trailer? Pass.
The other thing that wasn't great was helmets and little (<2 years) kids. The trailer didn't seem to be designed with helmets in mind. I expect the designers felt that a metal cage and a 5-point harness was enough protection, and I can't say I disagree. It's the law 'round here, though, so there you go. I don't know if it was a head control thing, or the fact that the back wall didn't have enough room for helmets (I suspect a bit of both), or something else, but the helmet thing was pretty unpopular at first. It got better as they got older.
It's very well thought out with built-in waterproof covers and insect screens. Sun protection is pretty good too. We went for the non-jogger version, so plenty of room for stuff in the back. I sometimes kick the back even at a brisk walk, though. I'm easy with the non-jogger thing, though. Jogging isn't my thing at all.
So, it's been pretty good. Yet we have a cargo bike now. Why?
One, we have three kids now, so a two-seat trailer wasn't going to cut it on its own. Two, dropping kids off in the morning and going on to work was time-consuming because I had to go home and drop the trailer off first. It doesn't cope well with narrow paths or cycle-calming measures either. There are a few places around here where it's either difficult or impossible to get a trailer through. It's difficult or impossible to get a double stroller through either, so boo to the council there.
The cargo bike's a pretty new thing, but it looks to be better for day-in, day-out commuting. I can ride it to work afterwards, for example, which never appealed with the trailer. I still think the trailer will earn its keep on the weekends.