I have the HP 4700 and like it.
Warning: don't expect this to be reliable. Windoze 2000/XP isn't reliable but a PDA is a couple of orders below that. The whole pocket/pc / windows mobile system is a piece of cr*p. I have been using PDAs for several years and they are OK for very specific applications. As soon as you start to load them up with stuff, they become very unreliable.
Tonight I have to drive about 100 miles somewhere, then more tomorrow, then a lot more on Saturday. I had TomTom 5 installed on the HP 4700. It never ran for more than 30 mins without totally crashing, but now it has just stopped accessing the GPS receiver. Other apps I have on it (Oziexplorer, Memory Map) use the GPS receiver just fine. A reset doesn't help, neither does a restore of a known working config from an SD card.
Luckily I am able to borrow my partner's Mitac 168 with TT3 on it. TT3 is a lot better than TT5 (well it works, for a start).
A PDA is a toy designed for business executives performing a narrow range of tasks, for which it can excel.