I have this version:
http://www.standingroomtents.com/ .
It works very well for what it is.
Pros:
It's a cube, so you get full use of the entire square footage.
Headroom is excellent, being able to stand up fully is an underrated experience in a tent.
Setup is quick, it just clips on to the pop-up supports. If your pop-up frame is sufficiently heavy, staking is optional.
This one has 4 doors/windows, which is great in high desert and other hot environments. Lots of airflow.
Also, makes egress/entry easy if the tent is full of cots, etc. Pick the door that's most convenient.
Goes up essentially as fast as your pop-up.
Pop-up frame provides plenty of attachment points for gear.
Cons:
Cheap pop-ups are inherently flimsy, and the frame provides all the structure.
It doesn't deal well with uneven ground, you need a pretty square, level spot.
Rain is an issue like with all pop-ups if you leave the canopy top on.
The square sides make pretty good sails if the wind kicks up.
We have camped in ours 2 or 3 times a year for longer trips when having more space is important, but we don't want to put up the really big tent.
It can get a little chilly, since there's a lot of space to warm up.
If you regularly camp at established camps, I'd look into it more. I would not consider it for boondocking or unimproved camps.