Well Savage, since I happen to work for a LARGE wireless carrier, I'd like to offer a few suggestions.
We do not carry any Sony Ericsson devices, so I cannot specifically speak to them, but I've heard different opinions on them. That being said, I truly do not believe you will ever get a majority of people believing one model device is outright better than the rest. Every wireless device out there has it's positives and negatives, it really depends on how you will use it and what you want or need it to do.
There are some things, though, that will affect phones that you may want to consider before laying down your money. Every carrier today runs a digital network, which means you can get all that cool stuff on your phone now like video, streaming radio, TV, web access, etc. Digital networks also operate more efficiently than older analog systems, so typically your battery will last longer, but again, how you use your phone plays into that. If you use the data capabilities on your device a lot, you will burn your battery faster. If you have a phone that can work on analog systems (they'll say dual band/tri mode) and you are on that analog system, your battery will be used up twice as fast because the phone has to work twice as hard to maintain that connection.
Aside from form factor and aesthetics, the quality of the radio is what determines how well the phone will "grab" signal. Many, many people believe that if their phone drops calls or cannot "see" signal, that it's the network. True, there are times that is the case, but the vast majority of problems are tied to the phone itself. Just like any RC transmitter, car stereo, wireless phone, cell phones have a radio in them with a crystal designed to work on a particular carrier (which is why you can't take your phone from one carrier to another). Some cell phone manufacturers have great radios (Sanyo, Samsung, Motorola and Audiovox have good radios). Others have fair radios and still others have, in my opinion and experience, absolutely horrible radios (LG Electronics). In my opinion, what's important to consider is the where and the how first, then start adding features. With the ability to keep your cell phone number no matter who you use as a carrier, you don't necessarily have to feel trapped only by what your current carrier has. Yeah, every carrier has a contract and an early termination fee, but every carrier also has credits and discounts for signing up for new service that usually offsets the term. fee.
As to your specific question (after I've babbled on), I've heard favorable things about the Sony devices. Motorola, as had been mentioned, is another that gets good reviews. Personally, when I'm working with a client, anything made by Sanyo or Samsung are the ones I suggest first. Motorola ranks a close second and the others kind of trickle in after that.
One last thing, then I'll shut up. Whatever you get, always ask how the phone gets its updates when new towers are brough on-air. Sometimes you have to call and have your line flagged, sometimes its automatic. It's just good to know.
Oh, and if you're wondering who I work for, well, if I had my druthers, I'd of named us Sextel!