I have the Instinct... a few things I don't like about it...
No tethered modem support, although people have gotten it to work it's not support by Sprint and you risk violating the TOS and having your contract terminated.
Doesn't even include an application to read text documents, let alone word documents, excel, pdf, etc.
The camera is pretty bad unless you're in daylight. If you email pictures to someone, it emails links to the pictures on sprint's website... not the actual .jpg.
The web browser is in dire need of improvement... you can browse most pages, but you'll find that a lot of links don't work. For example, I can browse AT's forums and even post... but if I want to reply to or quote a post in the middle of a thread, the Reply, Quote, Top, Bottom links don't work. Have to use the ones in the original post for it to work.
There's no file browser for the memory card.
There are still no useful applications available for it, including Instant Messaging.
The reason I got it was that Sprint's Everything Plan is superior to other companies. 450 anytime minutes, everything else is unlimited... Nights/Weekends, Text, Data, GPS Navigation, etc. for $70 month. The closest I could find was a plan from Verizon for $85/mo I believe.
If Sprint would add official tethered modem support I'd be ecstatic.