After a few days of playing around with my T68i I came to the same conclusion.
Reception was bad. In the area where I live reception isn't all that good to begin with, but it made a turn for the worse with the T68i. This was one of the exact reasons I wanted to upgrade from my former phone, a Nokia 8810 (a phone known for it's bad reception).
Another problem I had with the T68i (but this one's purely subjective) : I found it weighed to little. I'd keep it in my pocket, but it weighs so damn little that I kept on feeling in my pocket if I hadn't lost it or something. Very annoying.

So I returned the phone to the shop last week, where they were so kind to completely refund me. I was so impressed with this service that I ordered a Nokia 7650 right there on the spot. I knew by reading this thread this was much more the kind of phone for me. And I've always liked Nokia better anyway.
Only downside was I had to order it, because the 7650 is (once again), still unavailable in Belgium. *sigh*