I bought my event shelter for a birthday party in case it rained. It didn't rain, but it looked fantastic with the lights and balloons in it anyway.
The day after the party, it started raining, and has barely stopped in the 3 weeks since, so I've ended up leaving it up the whole time. Not only have I enjoyed being outside in the rain under it, but now the sun has finally come out, it's proving to be a great sunblocker too. It's still lovely and bright under there, but I can actually work on my laptop outside too, as it takes away the glare.
As for the build and quality etc - we had difficulty working out the pictorial instructions, but once we decided to just ignore them and work it out for ourselves, we had it up within a few minutes. We couldn't quite get one side to stretch over the poles correctly and had to just leave it loose on that side in the end - probably due to us getting it wrong rather than anything wrong with the structure itself. It's ended up staying that way these 3 weeks and hasn't suffered for it.
We've got it up on our (large) deck, so we've had to tether the guy ropes to rocks, garden benches etc, although there is also the option to screw it down as each of the feet has 4 holes in it for securing with tent pegs, but you could easily use large screws instead for a more permanent fitting.
I would definitely recommend this product!