"I got two of these and the cats like them.
I did not have any of the installation issues noted by other users, and I used the velcro strips included.
This is reasonably attractive and the cats like it. The only color option online is navy blue. The small cat jumps up unassisted. The (ahem) larger cat prefers having a chair nearby to use as a step up. I gave it 4 stars because I have seen better cat window seats, and most cats I've met seem to prefer a sling or hammock style perch to a plat padded bench.
Regarding the velcro issue:
The velcro is pretty strong, but it is supposed to stabilize the seat rather than provide structural support. Before attaching anything, wash and dry the sill to remove any dirt or dust that will interfere with adhesion of the velcro. It helps if the seat is pushed towards the window as far as it can go, and if the legs are adjusted so that the seat tilts ever so slightly towards the window. Also, don't try to separate the two sides of the velcro before positioning the seat. Just peel the backing off, position the seat and stick the entire thing on as one piece. You'll be able to apply more even pressure on the velcro tape by pressing the seat. Hope this helps."