The hardware
Make no mistake - the PSP Go is a gorgeous device. It's smaller and lighter than previous PSPs, making it by far the most "pocket friendly" model yet. The 3.8-inch LCD, while half an inch smaller than previous PSPs, retains the 480 x 272 resolution of old, meaning a crisper looking screen thanks to the increased pixel density.
The only addition in terms of hardware is the inclusion of Bluetooth 3.0. This allows you to pair up with Bluetooth stereo headphones, tether to a laptop or cell phone for Internet access, and even pair with a PlayStation 3 controller (Sixaxis or DualShock 3) and play your PSP games with a "real" controller. Combined with a TV-out cable, this is as close as you're getting to a portable games console without consulting someone like legendary modder Ben Heckendorn.
The mechanism that slides the screen up to reveal the controls feels sturdy enough to go the distance, and even survive a drop or two while open. The controls themselves have been changed significantly from prior models, with the directional pad and face buttons sporting a much clickier feel, which I think is a big improvement.
Unfortunately, the face buttons are much smaller and closer together than before, which isn't too much of an issue until you try to hold your thumb over two buttons at once (think: driving games) which I found hard to get used to. The analog "nub" is smaller than ever, but didn't require any getting used to - I actually find it far easier to operate than the awkward placement of the old PSPs.
One area that sadly hasn't seen any change in all three revisions of the PSP is the Wi-Fi. The brand-new PSP Go is stuck using the nine-year-old 802.11b standard, and it's incapable of dealing with WPA2 encryption, which is the only totally secure Wi-Fi protocol around. For a device released in the second half of 2009, that uses digital distribution instead of physical media, this strikes me as utterly crazy.
And then we get to the omissions. Gone is the mini-USB port, meaning not only will you need a proprietary cable to charge your PSP Go, but none of the existing PSP accessories like the camera or GPS will work without the purchase of a ridiculous-looking adapter. Also gone is the replaceable battery, meaning that with a maximum of six hours battery life, the PSP Go won't go the distance on a long-haul flight - until the third-party accessory-makers bring something to the table. The battery decision was no doubt to make the "Pandora's Battery" hack much harder (perhaps impossible?) to perform (hackers discovered that a modified battery can be used to install custom firmware onto the PSP, enabling easy piracy).
The software
There's still a dated web browser, a sub-par media player with just-average format support, and an inability to download in the background or resume downloads should they fail for whatever reason. The one addition I can find is the ability to pause a game, hit the XMB (that's "menu" in Sony-speak, for the uninformed) to listen to music or watch a movie (or whatever), and then resume your game without actually having to use the in-game save functionality - which is a reasonably useful addition, as some developers haven't quite grasped the concept that people playing their games on the move might not always be able to play for another ten minutes to reach the next save point.
The games
The maximum UMD can hold is 1.8GB, so you'll fit at least eight games on the internal storage of the PSP Go - but you're likely to fit a few more on there than that, with the content-heavy Gran Turismo weighing in at just over 1GB.
There's more than 300 games available on the PlayStation Network (versus the 600+ available on UMD), and while all first-party titles will be released simultaneously on UMD and the PlayStation Network (PSN), Sony is not requiring third-parties to release games onto the PSN - and there's already instances of publishers saying "no thanks" to PSN versions of their UMD releases.
Unfortunately, it's not just the number of games to choose from that will be impacted by choosing a PSP Go - it's the cost of them. Of course, you're not going to be able to pick up second-hand UMDs on the cheap, but you already knew that. What you might not know is that Sony has announced plans to keep PSN pricing at parity with the MSRP on UMDs. So while the retailers aggressively promote discount prices on new releases and older titles, you're stuck paying a premium on a product that costs far less to provide than the boxed physical media with printed manual.
The price, and the lowdown
The PSP Go costs a staggering US$250 (versus US$170 for the PSP 3000). That's just $50 shy of the 120GB PlayStation 3 Slim. When you consider the fact that a PSP 3000 with a 16GB Memory Stick Pro Duo costs $20 less than the bare PSP Go, and can still play games downloaded from the PSN, I'm not entirely sure that the suits at Sony hasn't taken on board Dan Ariely's conclusion that, to paraphrase, offering people a bad option makes most of those people choose the good option.
Nevertheless, it's frustrating to see how close Sony is to having a game-changing device. Put in a decent wireless chipset, a capacitive touch-screen, an accelerometer, a camera with autofocus, and a second analog nub and you would have a killer device worth paying the premium for. Address the software issues with a WebKit-based browser, decent codec support and a quality media player, and you have something that could be a serious contender in the PMP market.
So, who's going to want a PSP Go? If you're a newcomer to the PSP platform, don't mind not being able to extend the battery life (yet), like the idea of a very portable device that plays the best quality games you're likely to find on a portable device for some time, and don't mind paying a premium for a smaller selection of those games, then the PSP Go is for you. Everyone else is more likely to find joy in one of the previous PSP models - I'll keep loving my PSP Slim (it's always the first thing I pack for a trip) until the PSP2 arrives.