Having owned the previous PSP for nearly a year I traded mine in for the new 'Slim & Light' version a few weeks ago. I'm an adult that travels a lot so for me the reduction in weight (by a 1/3) makes a nice difference in my bag and the ability to charge from USB also means I no longer need to carry the charger on longer trips. Sony claim to have made the internal electronics more efficient so the smaller battery doesn't affect 'play time' and I have to agree; if anything I get more use out of a single full charge - maybe as much as 15-20% over the last model. The web browser is also faster (and doesn't seem to run out of memory any more) as well as games loading a little quicker.
The original felt so substantial that at first the new one seems flimsy - but don't be fooled into thinking light can't be strong, it really is just as sturdy.
On the plus side, the weight, screen, battery life, USB charging & extra memory are all nice to have and I really welcome the fact that there are no dead pixels on the screen of the new one.
A neutral point for me is the video out - I suspect it won't be used much for games but if you have video or family shots then it makes a nice portable player for that sort of thing and the MS Duo cards are now coming down in price (I have 2 4GB ones and watch quite a bit of video on the move).
Why not five stars? I'm not sure I like the shiny back instead of the old matt finish and USB charging only works in 'USB mode' meaning you can't use it while charging via USB or charge via USB if the battery goes completely flat.
The other comment that 'it still only plays the same old games' is a platform decision, if you don't like the games get a different portable player. I love my PSP for First Person shooters, videos and podcasts downloaded directly to my PSP at home.