I used to have an Ericsson T18z. Like Pradeep's recent model, the RF performance was amazing. I could get and retain signals in places most people couldn't. Unfortunately, it was digital only, which meant that it couldn't be used in rural areas where there are only analog cells. Beautifully compact and brilliant in its reception. Not many features except for voice-activated dialing (useful when you're in the car).
I now have a Samsung SCH-8500 like Fushigi. Average performance and clarity, but the good thing about it is that its microphone is not very sensitive, and you can thus use it in noisy areas... people usually have no idea you're outside on a busy street. Built like a tank. Dropping it on the ground inflicts more damage on the concrete than on this phone. I was comparing it against the Motorla StarTAC at the time. The StarTAC felt like it would break after a day in my backpack.
I now crave PDA features in my phone and am considering a Kyocera 7135. I find my Sony CLIE very useful, but the problem is that I don't have anywhere to put my PDA. It's already a pain to keep my cellphone on me at all times (I am not a big fan of belt clips/holsters and most phones are too big and heavy to put in my pocket comfortably). Now adding a PDA to that? I might as well carry a man-purse to hold all this crap!
The Treo is very nice as a PDA, but I find it awkward as a phone. Most of them you need to use a headset anyways.