honestly, it's kind of a rip-off - you can make a playpen for rats for a whole lot less than $44.99 +shipping and you can buy a playpen for bunnies for around the same price that's infinitely better.
for $10 less than the "grrreat wall", you could get a
30'' tall playpen - which provides about 64 square feet of space - more than 3x the amount of the wall - and it would also be taller. if your bunny is a jumper,
this pen is available in heights up to 48'' and is the best deal I've seen on a pen that's higher than 30''. Both pens come with FREE shipping... as opposed to the GRRReat wall, which is $13.99 shipping for one, at least to my zipcode. I used two of the 48'' high pens to fence in my whole living room for my bunnies (I went with the tallest one so I could put big cardboard boxes and such in there for them to play with).
for rats, you can buy two 3'x6' sheets of coroplast (corrugated plastic) from Home Depot for < $25. cut each sheet into thirds and you get six 2' tall by 3' wide "walls", which would make a play space that's just over 23 square feet - bigger than the space a grrreat wall creates and $20 cheaper. here's a tutorial on making a coroplast playpen for small animals that are climbers -
http://hamsterhideout.com/forum/index.php?showtopic=67463.
[edit: by the way, you need to ask where the *plexiglass* is when you go to Home Depot - 9 times out of 10, an employee won't know what you're talking about and/or will tell you they don't sell it if you ask for coroplast]
if you bought a playpen for your rabbit and two sheets of coroplast to make your own playpen for your rats, it would come out significantly cheaper than getting two of the walls... and with the walls, you'd need a lot more than just one to create an area that was suitably large for a bunny.