No I was referring to when I leave them all uncheked. Others said it forced to 567p but my TV always outputted at 1080p so I presume my display was doing its own upscaling and I wasn't aware that the PS3 was actually dropping to resolution down.
Will have to do some testing tonight.
Best thing to do, IMO, is tick the boxes your display supports.
If it's 720p, it'll display 720p and your display will scale it, if it's a 1080p game, it'll display in 1080p.
But yep, some people have disabled 720p, to make the PS3 output the games at 1080p instead. I think many times this works, but sometimes it'll drop it down to 576p.
Still, on my two displays, as I said, outputting a 720p game at 720p and letting the display scale it, looks better than when the PS3 outputs a 720p game at 1080p.
Maybe this varies from display to display, or maybe some people think a higher number is better... ie, if the PS3 is outputting 1080p this must be better. Of course, the game is still only rendered at 720p, it's not like a PC game, where you're changing the resolution.
I'm playing Resi 5 right now, my 1080p TV is running at 720p, and it looks fine

(as it's meant to) I don't want the PS3 to scale anything, it's a 720p game, and my TV is running in 720p mode.
Vin.