I have mine at about 11' away and - at nearly full zoom - I get about a 105" screen. I do notice a drop in brightness when I zoom but it's very negligible. Changing the settings manually or fiddling with the dynamic settings will alter the brightness much more than zooming. I will try and take a photo later to show this but I don't know how well it will work
As for daytime viewing I have tried and it's fine but only if I close the curtains. Sky+ (not HD) is certainly viewable without any real issues but black levels really do suffer under these conditions. I don't really think I'll be using it during the daytime so it isn't an issue for me. If it was a priority then I would probably want a projecter with a higher lumens rating. Once it's evening or the room is darker then all the problems go away and I'm left with a stunning image

The projector is easily bright enough for movies, games, Sky etc