To me, the size of the
Wireless Keypad is a drawback. Not an insurmountable one, but the keyboard is a bit small. I would prefer a full size keyboard, personally, but the keys are a reasonable size for a mobile device, and I get the feeling that's sort of what they were going for.
The attachment is strong. I haven't had any problem with the device slipping off or moving around when I was using it or the controller. As well as it holds, however, it is easy to remove when I want to remove it, so this functionality is pretty much perfect.
As for the location of the keypad, it's in a relatively accessible location, if you are going to type with your thumbs. This seems the most natural way to use the Wireless Keypad, since the keyboard is too small for a human hand to practice "correct" typing on it. I find that I sort of "swap" between "keyboard" mode and "analog stick" mode when I use the keyboard, so I wouldn't suggest trying to run around or look around while typing, so, again, this is not the answer to your needs to time-critical in-game communication.
The mousing feature was a surprise to me. It seemed novel in concept, but, after using it, it still came off as sort of a novelty. Before you use the mousing feature, you have to "initialize" it by pressing and holding two buttons specifically included for this purpose until a certain light blinks. Any attempt to use the mouse feature before initializing the keyboard results in wild, uncontrollable mouse movements. After initializing the keypad, the control tightens up... a little. In my trials, I found that when setup, I could get the pointer to go where I wanted it to, with some difficulty. However, there doesn't seem to be a way to "click" on something other than using the Wireless Keypad's (Enter) key or the gamepad's (X) button, as normal. Also, the Wireless Keypad's mousing feature is so sensitive that the pointer would often move in the process of me lifting my finger off of the keys to move and press the (X) button. While it's possible to use the mousing feature, the analog sticks are simpler. There may be a learning curve that applies here, but I don't really have that big of a problem with the analog sticks. At the very least, they're not the biggest gripe I have about trying to surf the web on my PS3.
I hesitate to take off many points for a tricky mousing feature, since mousing is a tossed-in feature that can be turned off. The keyboard itself serves it purpose well, and the design doesn't use up your gamepad's battery charge or interfere with your normal control, which is nice.
The places where the Wireless Keypad seemed to let me down weren't really its fault as much as it was the fault of the software. Web browsing with the Keypad was fine - even the mousing was reasonable - at times. However, when I went to enter a code to redeem it for a credit for a game, I found that I had to select each section of the code, individually, and only then could I fill each section out. Once filled out, I couldn't simply use the Keypad's (Tab) key to advance, either. When entering codes to be redeemed, the Wireless Keypad seemed no more efficient than the virtual keyboard. Hopefully, Sony will address the text controls for these codes and make them more Wireless Keypad friendly.
All in all, the Wireless Keypad is what it is; if you want a PC-type experience out of your PS3, you need to go ahead and get a full-sized keyboard for your keyboard input and, well, I don't really know what to tell you for your mousing input. If you're looking for rapid-paced communication with friends in-game, you're going to want to pick up a headset, instead. If the idea of a small keyboard attached to your controller sounds like what you're looking for, then Sony's Wireless Keypad might be just what you're looking for. And there's even some touchy-feely mousing action for you to play around with, if you're into that.
