I borrowed my N610C from my daughter the other day. I had used it for 1 1/2 years, so I was quite familiar with it.
Anyway, in using it again, a couple of TG50 advantages that I haven't seen mentioned became evident to me:
1) You can hit the Home button with your left thumb (I'm right-handed). This has become my normal way of pushing this button. One less reason to pull out the stylus.
2) You can use the up/down button with your left thumb too. I *hated* the up/down button as much as anybody, but I have to admit that it's much easier to use with your left thumb, once you develop the required callus. This is somewhat important as the scroll-wheel does not always do what I want. Usually the up/down is a full-page scroll, and the scroll-wheel is a line scroll.
Somewhat off-topic: I used to think my N610C had a great screen. It looks terrible now (milky and indistinct, and much dimmer) that I'm used to my TG50.
Yes, I agree with you, TG50 is one-handed, especially when with Keyquick installed, I can input data, launching program, controlling playback of MP3s with my left thumb, I only use my stylus when playing games