Well, the opus had some nasty bugs at first. Bookeen fixed that

Bookeen is sometimes slow with updates, but bugs gets fixed, and they add features every now and then. Sony is mostly happy with just bug fixes.
AS PRS-T1 owner, i'll still get the odyssey. The T1 is a good reader, but it lacks folder view. That's kind of a show stopper for me.
Odyssey have hyphenation that's a definitive plus. I like the rendering on the orizon better than the T1.
But i would say the T1 beats the odyssey for notes and music and dictionary. (we'll see when the odyssey comes out).
Honestly, T1 and odyssey are both good readers, i don't believe you can be wrong with either of them.