I recently purchased an HTC PPC6800 Mogul and I could not be happier with the purchase. My last two phones I have purchased through Ebay and have had no problems at all with the phones. My Mogul solves all of the deficiencies I had with my last phone, a Treo 650.
The Mogul has a side slide keyboard that easily accommodates my large fingers, it has a very good camera taking both stills and movies and has an LED flash. It doesn't use a regular size SD car, it uses the MicroSD card. I currently have a 2 gig holding all my music and a few games and have about 800Megs still available. I bought the card for $10 and it came with an SD card adapter so it is extremely easy to use. It has a switch that uses WiFi or wireless internet connections, in addition to connecting to the 3G network so the internet is always available. The software is Windows Mobile 6.0 or 6.1 so it is very familiar to most users. The speaker for listening to MP3's is very good considering the size and the earbuds are even better. I haven't started using the Email feature but it is available if needed. HTC has one of the largest touch screens available on the market and it is accurate and easy to use with either the stylus or even your finger.
Basically, I highly recommend researching the HTC line up, LisaG helped me a great deal when I first came here and knows what she is talking about.
My only complaint about Sprint is that it is difficult to transfer contacts between phones. The HTC makes it easier because it had IR and you can just beam the contacts over if the old phone has IR.