I have them although haven't put them up in this house as they would need adjusting to my windows - my solution now is simply not to open the windows as I'm petrified of spiders coming in the house in any case so they're locked shut even in the height of summer
The mesh I have (standard fibreglass mesh in black) is fairly tough ie if he skidded on the windowsill he wouldn't go through it BUT it doesn't stand up to cats climbing up it very well
When the boys were around 6 months old (so as heavy as an adult) Lukey climbed up one and it had pinprick holes from his claws, nothing serious enough to compromise the mesh but it would have been if he'd carried on climbing them.
If you have any climbers then I'd defo go for the aluminium mesh but it is slighty more obtrusive I believe than the black mesh. I'm sure they sent me samples of the mesh to look at when I emailed them.
Mine were secured with the velcro to frame method, I was worried that wouldn't be secure but it was very strong stuff and no way would they come off with velcro on all four corners. As I said, they're not up in this house so can't take any pics but will see if I have any old pics from before, I'm sure I took some to show my Mum when I first got them.