We are really happy with this trailer. We haven't used it as a stroller so can't comment on that, but as a bike trailer it is excellent value for money. My husband tows it, he say it is heavy to pull, but the more we have been out, the easier it got.
Good points : It is well ventilated so our son stays cool when the weather is hot. The wheelguard bars stop the wheels from being damaged if you ram something (our friends have a trailer without bars and the wheels buckled). If you need to make it narrow to fit through a gate the bars are detatched easily. The whole trailer is very sturdy and excellent quality. It has a proper seat that is higher than the footwell (this seems obvious, but we have used trailers in the past that don't have a seat as such, the seat is literally the bottom of the trailer)so it seems very comfortable. It all fits easily into our car boot, which isn't massive. The trailer is quite spacious, bigger than others we have used, so although we haven't tried to put 2 children in it, it seems that it wouldn't be a squish if we did. The storage at the back is roomy enough for 2 rucksacks.
Not so good points : As already stated, it can be a bit heavy to pull. It is not so comfortable for our son if he falls asleep in it, we have to prop him up on a rucksack or lay him down on the seat. I'm sure also that the flag only attaches on the left of the trailer, which seems like the wrong side to me if you were pulling it on the road.
I suppose though, that the telling sign on how comfortable it is, is that my son loves being in it. "faster daddy" he calls. Its alright for him, he doesn't have to pull it.