The PSP has been very hot and cold, though. Its fine one minute, down the next, then back up again. Its not threatening the DS's marketshare as the damage has been done. It was done a loooong time, ago. (I'm not saying that the PSP is a flop, but just pointing out how much of a behemoth the DS has been...it's been unstoppable for most of its lifespan. 60 million units for the PSP is great, though.)
Sure, they'd want to get the PSP2 out as soon as possible, but the hype for the 3DS has been going for quite a while, and (correct me if I'm wrong) but have we seen the PSP2 yet? As powerful as the PSP2 will be, it hasn't got the same kind of wow factor that Nintendo have managed to obtain with the 3D sans glasses. So, I think they can afford to hold off for slightly longer. Especially to get things right. Seems very rushed, atm.
I know they have to strike whilst the iron is hot. But, you can only launch a console or handheld once, so you may as well make the most of it. In my opinion, the release date is simply too soon and the price is too high. Like you, I'd fancy a September-ish date, maybe a bit sooner. Take 50 quid off that price and I'd love to own the system. That is a lot of money.