Bottom line, if you are going to be typing a lot on the PS3 then you need this. Yes you could use a full keyboard but that means 1) using a USB slot and 2) having a massive keyboard lying around.
This offers a small, compact keyboard always attached to your controller. Its pretty simple to use and works like any keyboard would.
Only down sides..
1) Te keys are a tad small, and it takes a bit of pressure to ensure they respond with letters.
2) The "mouse style" directing thing which you activate by pressing a "finger icon" at the bottom is pretty much useless. But you have direction buttons to move the cursor anyway.
3) It has to be charged seperately from the controller. This is both food and bad. Bad that you have to charge it seperately, but good that it wont eat the controller power up.
Otherwise, its basically worth it to type easier, and definitely get it from play.com beacuse highstreet stores are A LOT more expensive.