I used compaq and after the hp takeover hp ipaq pda's now over 13 years, the are very durable, well build and the windows based OS is very compatible with any windows based comp. The active-sync program works well and fast, the unit I have right now (5 years old) has a SD and CompactFlash expansion slots, besides that it has bluetooth, the processor is quick. I like the Windows OS, it runs all Microsoft Office products seamless I even run Power-point presentations in my meetings straight into the projector. the only thing I miss is wifi and I would be all set.
It early depends what you are looking for, I choose a model without phone capacities, when I'm off I do not need all this info and just want to carry around my mobile phone, but if you need both combined I advise you to go with one of the Blackberry models.