Others say...

"Falls apart easily"
My son solved the 3x3x3 so I bought him the 4x4x4 and 5x5x5 versions for Christmas. I have had to reassemble the 4x4 and 5x5 numerous times within 1 week of him receiving them. He is very careful with them but still they fall apart easily. It is just a matter of time before I pitch both into the trash.

"The #1 Hit for Christmas... even over a much longed for Video Cam!!!"
Our 10 year old son has been asking for a video camera for 2 years. We finally got it this year for him as his big Christmas gift. Rubik's cubes have also apparently come back strong. He has been asking for one for a month or two. Naturally, I expected it to be a short-lived fad that would fade in comparison to his much longed-for video camera. To my suprise, after a day of contemplation the kids were all asked what their favorite gifts were. As we tucked him in, our son kept saying how he couldn't wait to go back to school to show everyone his 5x5 Rubiks cube. It's all he did all day and seems we're in for a lot more. It also stood up to his "learning" how to take it apart and put it back together (his 3x3 didn't survive that learning). Seems like a winner so far!

"Excusable fragility."
This cube is a lot of fun. Once I got to about 30 seconds on the 3x3 cube, it was time to move to something harder.
Yes, when I started my Professor Cube the stickers started peeling off very quickly. However, I expected this. Unfortunately, Rubik's has been using pretty crappy stickers for a while now. They're basically white stickers with mediocre paint on them, covered with a square of plastic. The plastic falls off and the paint wipes away. Many avid cubers will either make their own stickers or buy the pvc stickers direct from Rubik's. While extra expenses are unacceptable, a true Rubik's Cube fanatic expects to be replacing stickers at some point. The pvc stickers are so great, I probably would have done it sooner anyway.
A lot of people are complaining about the fact that the cube falls apart when turning the layers while misaligned. While I understand the annoyance (and had to deal with it myself plenty), I can't rightfully fault the product for that flaw. Looking at the 3x3 cube's structural design, it makes sense that it doesn't generally fall apart when being solved. Now look at the design of the 5x5. It's insane. It's basically a ball with a ton of precise pieces that hold each other together. The fact of the matter is, there's no better way to make this cube while still maintaining full usability. It was made out of demand and the right people will still buy the Professor Cube.

By the way, it's hard to call this a toy. It definitely IS fragile and a vast majority of people will never be able to solve it. At least with the 3x3 it'll stay together. Unless you're really up for a monstrous challenge and tons of frustration, don't buy this product. It WILL fall apart occasionally, you WILL have to buy new stickers, it's a HUGE pain trying to put it back together, and most people will likely NEVER solve it.

But hey, it's a hell of a conversation piece.

"For the price I expected more"
The product is quite expensive. but the pieces are almost breaking, the colors are just stickers - ready to fall. I expected more from for the price I payed

"Just be careful"
I don't know if it's a matter of defective items, or differing ideas of what it means to treat a cube gently, or what, but I've had none of the problems reported here with this cube breaking so far. One cubie did start to pop loose one time, but I pressed it back in and it was fine. Yes, this is less robust than the order 4 (Rubik's Revenge) cube which in turn is less sturdy than the order 3 (Rubik's Cube); yes, you do have to be more careful with it; no, you can't speed cube with it. But mine isn't prone to breaking under gentle use. Nor are the stickers peeling off.

I figured Rubik's Cube out on my own, many years ago (not from a book), and when I bought the order 4 cube I found there was much that carried over from the order 3, but there were new problems to be solved too. Proceeding then to the order 5 (Professor) cube, it seems to me there's nothing really new if you have a good understanding of how to attack the order 3 and 4 cubes. There are more cubies to deal with, but nothing fundamentally different. I unscrambled mine the first time in under an hour -- and that's with treating the puzzle gently, and my own lack of speed generally, and a few times I made mistakes and messed up some of the progress I've made. So, if you're looking for a new level of intellectual challenge, this isn't it. And, obviously, it's not for you if you're obsessed with speed.

On the other hand, if you just like unscrambling the lower order cubes just for the mental calisthenics of it, this is a good puzzle. And obviously if you're into pretty patterns, or if you're simply a cube completist, you'll want an order 5.

Just treat it gently, and I think you'll be happy.