I was just about to post a similar thread!
Seneca Wallace is an unknown. The Seattle fansites sound like ours arguing about Beck/Lemon/Fiedler/whoever, where poor passing is alternately blamed on the QB or the WRs. Seneca apparently played well against the 9ners.
Positives - They can sack the QB decently (upper middle of the pack). They can run the ball with Julius Jones decently as well (they run a lot too). They don't make many penalties (are better then us at that, and we are pretty good!)
Their passing O sucks - they are towards the bottom of the league in total offense, passing offense, first down passes, total receptions, are about 50% on completions, etc.
Their TO according to NFL.com (i don't know if it was updated for yesterday's game) is -3.
Their passing D sucks too - They are sadly tied (again according to NFL.com) with us for numbe 1 in the league in receptions allowed over 20 yards. The yare tied with lions with 8 passes over 40 yards (we are at number 2 with 7). We seem to be improving though... Their run D isn't terrible, but that could be misleading because of their pass d.
They have Olindo Mare who has been playing well.
That;s just a few thoughts although I haven't really watched them play so it is guess work for me.