Sigh. I also haven't touched my PSP for very long long time - although I've been playing my GBA non-stop these days, thanks to the Castlevania double pack. I am seriously considering getting DS, but waiting for better looking revision (if there will be any). I thought watching movies on PSP was cool - but after a while the whole encoding and all just became tiresome. Homebrew was also neat, but not just enough to fill the void in. A lot of PSP games are done better on PS2... but I guess it's just my situation. I love the design and capability, but somehow it's missing something very integral part, the part that keeps me occupied on this cool looking machine though... maybe it's the library of games that I'm interested in a handheld machine, or what not.
Sure, PSP could sell and well over DS, but it's not the hardware numbers but more importanly, the software sales # matter IMHO. While DS's 1st party line up sells quite well - but some might say that 3rd party games do not sell well... I think it speaks nothing more than Nintendo's quality and understanding of providing good hand-held games - which is one of their strength, and an utter proof that the DS buyers are actually "game buying" public, and perhaps PSP buyers are more of "cool gadget" collectors to certain degree - and other PMP machines are now towering over PSP, I'm not sure how well this PSP being PMP plus near PS2 quality games merit will last to be honest.
And.. we shall never forget that we'll probably see the true successor of GBA in a couple of years...