The biggest problem with the PSP iTrip
may not actually be the unit itself, but more the PSP. If you already have a PSP and a 1GB MemoryStick Pro Duo, you can actually build a decent playlist. Those of us who haven't sprung for the big memory yet don't have much in the way of music on our PSPs. I have a 4GB iPod that I use in the car, and it's going to take a lot of scrilla to replace my iPod with my PSP. I would definitely listen to RSS streams (Podcasts) in my car with my PSP, but that's not happening until municipal wireless comes to my town or I get that big memory card.
So, the best use right now that I can see for the PSP iTrip is to enable folks who don't already have some MP3 player to rock their tunes in the car or at home. The idea of listening to RSS streams at home through a stereo is good, assuming that you have a wireless home network. If not podcasting, there's the idea of listening to movie or game audio through a home stereo, which may work for some people. For me, a portable system is about portability, so I'll take headphones in the dark for that immersive, private experience.
The actual construction of the unit is decent, and consistent with the other Griffin products I own for iPod. I wish, like its iPod counterparts, that the PSP iTrip were powered through USB. When the PSP iTrip is plugged in, no sound comes out of the PSP speakers, so the irony is that when you aren't transmitting on FM you have to use headphones or unplug the unit to hear sound.
The PSP iTrip is a decent accessory that may be just what the doctor ordered for you folks with lots of memory and songs and a long commute. As memory gets cheaper - there's a 4GB accessory on the way soon, priced at around $150 - there's no doubt that this could be a useful gadget. Unless you really have to have this exact functionality, it might make more sense to wait for the next iteration (which will hopefully be USB-powered) and some cheaper memory.