Beware the cellphone company that comes bearing gifts

I recently received postcards from AT&T informing me they'd be mailing me a free cellphone, the Sony T226, to replace the Sony Ericsson T68i I've been using for over a year and a half. Very suspicious--when's the last time the phone company did anything out of kindness? Not that I love my T68i. It has certain usability problems which I've lived with b/c I purchased it with a generous rebate and because sinking money into new cellphones is a waste of money.
I knew there was a catch, though, and Engadget exposed it. The replacement phones are compatible with the newer 850 Mhz spectrum in which AT&T Wireless is building out its GSM network, and the phones they're replacing are not. Perhaps this explains all of the complaints about AT&T Wireless's coverage in the Seattle area. The Sony T226 I'm receiving shortly will be less functional than my T68i and won't offer the Bluetooth compatibility needed for my headset.
That's evil, and it means I'll have to call and use my big, mean voice on some customer service rep shortly.
We have cellphones that shoot lousy photos, offer games, surf the web, play MP3s, change channels, and yet I've still not found a cellphone/service plan combination that excels at all of the features I desire most: compact form factor, long battery life, an awesome antenna, a usable interface for storing and finding phone numbers, and an affordable nationwide calling plan. Perhaps that's why I've been such a conservative cellphone buyer. I've owned only four cellphones in my life, and two were replacements for one I lost and one I crushed in a snowboarding incident in a half-pipe. Am I jealous of those around me who flip to new phones seemingly every 8 months? A bit, though the cost that people sink into new cellphones is ridiculous (you either pay for it in the phone or, if the phone is free after rebates, in the long-term plans they lock you into).
Nokia's phones have impressed me the most, though their antennas haven't blown me away and their feature set usually lags the competition. But Nokia's on-screen interface is the most usable. Motorola has strong antennas but lousy battery life and a terrible on-screen interface. As cellphone functionality has broadened, the user interfaces have suffered. With my T68i on its last legs, though, it's time to dip back into the marketplace. I can even switch service providers with no penalty as I've been month-to-month with AT&T Wireless for quite some time now.
Has anyone had a good experience with a nationwide cellphone plan?