The first downside of the redesign is that the screen has shrunk from 4.8in to 3.78in, with the resolution sticking at 480 x 272. This isn't a disaster; this size/resolution combo works well for games and movie-watching, and this is actually the clearest, brightest PSP screen yet, with no sign of the weird heavy lines, interlacing issue that plagued the otherwise brilliant screen on the PSP 3000. The PSP was one of the few mobile media players - the iPod touch and the Archos 5 being other examples - where I have happily sat and watched whole films on it. I can comfortably say the same of the PSPgo. As a nice touch, the back of the case has two curved, rubberized ridges that should help hold the unit in place on a table or your knee while you're travelling around.
There are a handful of other changes. With less room on the face, the brightness, volume and sound buttons have been moved to a space between the shoulder buttons, leaving the home button the only real control left by the screen. The old mini-USB connector has been swapped for a proprietary socket, and you use the USB cable provided either with a PC or with the supplied USB charger to charge the unit. The optional AV cable now connects to this, and not a separate AV output socket.
The microphone and speakers remain, meaning the PSPgo will still operate as a Skype phone, and the PSPgo now supports Bluetooth 2.0 on top of 802.11b Wi-Fi, allowing you to hook up a headset or A2DP headphones if you have them (sadly, I don't have a pair to test this out), or a PS3 controller, though you'll need a PS3 to register the pad to the PSP. Be warned, meanwhile, that PSP accessories like the Go! Camera and Go Explore! GPS are incompatible with the new model.
The next major change concerns storage. It came as no surprise when Sony decided to jettison UMD; movie industry support had grown embarrassing and, in terms of performance, power usage and price, a move to flash memory is the right idea. The PSPgo ships with 16GB of the stuff built in, with the idea being that you download all your games and media and store it on the PSP itself. I don't think Sony has done itself any favours here by failing to find any way for existing PSP owners to transfer purchased games to the PSPgo, but otherwise this makes perfect sense.
Of course, there is a card slot to allow room for further expansion, but here Sony has shifted away from the old Memory Stick Pro Duo format to the Memory Stick Micro (M2) format. This annoyingly means you can't use your old PSP memory sticks or transfer any content you've already downloaded or transferred, but - to be fair - M2 sticks seem to be slightly cheaper at the same capacity than the old format. I know most of us would prefer Sony to move with the rest of the consumer electronics industry to MicroSD but, let's face it: that won't be happening any time soon.