I don't own one but did consider it. I decided against it for the following:
The zipper looked like a pain for access
Nylon mesh might be good but nothing beats aluminum screen for security when you have other animals
They look flimsy to me
With the above said I am genuinely interested in the opinion of someone who actually tried one as those are very uninformed opinions above and could be all wrong.
I have had a few in the past. Theres a couple things i dont like about them. 1. The zippers are kind of a pain. 2. Basking lights eventually make the material brown and brittle. 3. Visibility isnt as good as a screen enclosure.
They're zippers are a pain; the mesh is very dark so you can barely see inside; when you touch it you feel like it's about to topple over... The list goes on and on.
However, they are good points to them. They're cheap, they work, you can use them outside as a cheaper type of outdoor enclosure.