If you are thinking of upgrading to the PSPgo but have a load of old PSP accessories, there is a accessory that can help you out. The PSPgo Converter allows you to use accessories like the Go!Camera, GPS device and other devices. The converter costs $20 and makes the PSPgo less portable due to its large size. Of course, spending $20 is a lot cheaper than forking out on all the new accessories available, but there it would also be cheaper to just stick with your older PSP and make use of those UMD games you have lying around.
The PSPgo is small enough to fit in your pocket, however, this accessory bulks up the device and adds an inch to the height. While it could fit in large pockets, it also makes the PSPgo look much uglier. There is no word on a release date so you have a few weeks (or months) to contemplate getting one.