Aside from the practicality factor of having to carry all that stuff with you, I think it's more of a marketing issue than anything else. It's the possibility of saying "Look at all the things you can do it!" or "You can do everything with it". The main disadvantage is of course not being able to do any of it well, but it was the same with cell phones. Only recently have we been seeing cell phones that are good at browsing the internet or listening to music, but even each one of those has a main purpose... I mean, there's the "music series", "gps navigation series", "internet access series"... it's hard to do everything well, but It's also a way to keep the market active. What if Nokia or SE started to sell a device that did it all really well? Maybe they could do it, but would anybody buy anything else? It's the same with the PSP... maybe they could have released all of this before, or maybe even add a built-in camera on the PSP from the start, but what would they have now to add to the hype? Or to keep it?
I think all the stuff they're releasing (gps, camera, headset) had some way to be integrated into the PSP from the start, or into one single device. The reason that doesn't happen is mainly marketing... I mean, a 1.3 MP camera? How lame is that? Those have been around for years, now. How about a flash built into it? It's not that they can't do it, or it's too expensive... I can get a new cell phone with a 1.3 MP camera that costs the same as the PSP camera alone! ...but those things are left to be implemented in future versions... A drop at a time.
A more direct answer to the topic at hand: I'm not sure I'm willing to spend so much money on the camera. I'm trying the headset with Skype, but there isn't a lot of people I can call with it... I have a more flexible GPS system on my PDA... As for the PSP cradle, I'm sure that I wouldn't use it. When I'm travelling I don't have the oportunity to use such an elaborate set-up. When I'm at home, well... I have a TV, a computer, a nice sound system.... well, you know what I'm talking about
I would like to try all those things but it comes down to a question of cost. The geek factor alone isn't worth that much.