A couple of comments:

When I saw Expo, as I said before, his receiving looked good, his blocking of pitches in the dirt looked very good, but his arm did look erratic. His leadership skills looked excellent. He certainly has a strong enough arm to succeed in the majors, but I don't know enough about catching to be able to judge his capabilities in the finer nuances relative to the expectations at the level I saw him (game-calling, framing, etc.)

As for Kelly, let's go at this from 180 degrees opposite. Even Kelly has to realize that after the 2009 season he had on the mound, the organization is not going to back off the pitching side of this 2-way experiment, almost regardless of how he looks at bat and at SS. And since he distinguished himself on the mound, the organization is going to want him to raise his innings by, say, 25 or so this year. That means he is going to have to start at least as many times in 2010 and pitch an inning or more longer per start, or make about 4 more starts and squeeze his SS time even more next year. The Sox can try to keep up appearances on this, but the reality is that either Kelly is going to have to hit a wall on the mound very soon, or the SS part of the experiment is going to get squeezed out. If Kelly is going to develop as a pitcher, he has to DEVELOP as a pitcher.