Another advantage the PSP has over the DS is the ability to make a cheap alternative to the SK2/SK3 without the monthly bills. Bad news is it aint as mobile, as you gotta use a PSP at a wifi hotspot in order to make it work, like the SK2/SK3. and no vibration to alert for incoming mail/IM's.
I found a way to make AIM work on a PSP via the web browser. It's at AimOnPsp Right now I'm trying to figure how to grab AOL emails off the PSP and I dont want to deal with a PSP-only email account.
Remember these are not to replace a SK2/SK3, but for me I like the idea of making an alternative mobile communication device out of the PSP and not have to pay T-Mobile's monthly charges. Just the AIM on PSP website and a free wifi hotspot and I save myself $40 a month charges.
Just the keyboard input takes a bit getting used to, but oh well better than nothing.