Well this may not be a popular review but I thought I'd give my opinion after I found my dusty PSP at the back of a drawer.
After being caught up in the huge initial advertising and trying a PSP in the shop I got one when they came out in late 2005.
Since then it's had very little use as I find it very frustrating. I find that even though the screen is far larger than that of the DS I don't agree that it is easier to see. Even on the brightest setting I still find myself having to turn the lights off to see it properly at home. If you're outside or anywhere brightly lit then it's very hard to see at all. Just in case this was a fault I had it exchanged and found the replacement to be the same.
This analogue control is in a very awkward place and I found my thumb to be getting very sore after less than an hour's use each time.
Of the control buttons on the right, why do Sony see it necessary to use them for different functions to on the PS2? 'Select' on the PS2 control is 'back' on the PSP which means any PS2 user will keep de-selecting any options as the buttons are different.
While the sound through headphones is good quality (speakers are poor) it doesn't allow any decent volume to be achieved. This isn't so bad on games but for music or films in busy places it can mean not being able to hear very well, especially on quiet spoken parts of films where even full volume isn't nearly enough.
When watching films, again the screen brightness can be a problem, but additionally, having the chapter skipping operated by the corner control buttons means you often knock them and have to rewind back to your original place several times per film.
While it works well as a music player, albeit a very quiet one, it's a lot bigger than any ipod, and the limited battery life means you'll want to save your power for when you need the screen for games or films.
What else? Well even if you're careful, the screen sctratches VERY easily meaning you'll need additional protection, and with a lot of the aftermarket options being poor then you might have to buy several types before you find one you're happy with (I've tried four types of protectors/covers at around a tenner a go).
People seem happy with the browsing on the PSP. I've not tried that yet but I'd be interested to see how easy it is to use with no keyboard.
As for gameplay? Well here is where the PSP makes up for some of its' shortcomings. Games are certainly graphically impressive and very smooth. Sadly I can't comment on the playability as I find the controls too uncomfortable. Also with the dim screen and quiet sound the best place to play is at home, but if you already have a PS2 at home then why have a PSP at all?
Sorry that this is such a negative review but after such high expectations I feel very let down by what was delivered!
Sort the screen, sort the sound volume, give it bluetooth and a built in camera and maybe I'll be impressed, but until then it's not what I hope for.
It's undeniably a very cool looking toy, but now it just gathers dust next to last year's mobile.