I remember Seth filling in for an injured Jamie Nails at Left Guard in '03. Sometimes "ok", sometimes a turnstile in pass pro, and simply no push ever in the run game.
More of the same while starting at Center in '04. The best thing he could do was pull and get upfield, but once he got there he didn't do much.
But, he improved noticeably under Houck in '05, esp. in pass pro. Run blocking is still an issue tho. Kind of reminds me of Tim Ruddy in his latter years... "ok" in pass pro, but in spite of being a strong dude in the weight room, he can't translate it onto the field in the run game.
Bottom line: this is not the last OL addition this offseason. Seth will have to compete to start again, and this was a reasonable, essentially 1-yr deal.
I didn't vote because I don't feel the options fit the circumstances.