I have AND have used the following: These are my observations regarding the type of devices we're moving towards, so depending on how they are used and budget constraints others opinions may vary. Ask specific questions about any of them and I'll respond w/more detail if available.
Sprint Hitachi G1000, Kind of big and bulky, but nice screen size and features for what it is. (Definitely more of a data intended device than phone).
T-Mobile Pocket PC Phone Solid build, phone volume is a bit soft. Nice PDA form though. (Using as phone, grease from cheek/ear gets on display until you learn to hold it right).
Handspring Treo 300 Bulky, Plasticy, feels like more of a clumsy toy if comparing it to the PocketPC Phone. (works good as a Palm OS PDA though).
Two PDA/Phones I have on order and look forward to getting in are:
Kycoera 7135 and
Treo 600. These two look like perhaps the best form factor PDA/Phone combos yet IMO. There's also a Samsung with a Palm OS which is quite nice, but one of my users already has it so I'm going for the gear we don't have yet.
I'm also keeping my eye out for the
Xda II because it looks like an interesting beast.
Overall, we're going for units which are the most like good phones w/the functionality of PDA's. The latter two I've ordered seem to me to be the best moves in that direction thus far. Keep your eyes on what comes out of Europe as far as these devices go. They usually get the goods on these before we do. Ironic seeing as how their wireless technology sux compared to the US (I support 40+ field reps and 1/3 of them frequent Europe & various other countries).