I've been on Middlecoin continuous since last summer, and beta tested them with another address earlier in 2013. Others pools have popped up on occasion and I've tried most of them. Only Hashcows came close to matching Middlecoin's rate of payout averaged over a long span of time, but they haven't been the same since their holiday hack.
None of the other pools have Middlecoin's primary strength: H20dyssey's ability to sell coins when no one else can at a price no one can match. He manually trades like a hedgefund manager instead of just relying on Autotrade. High unexchanged is an artifact of this.
Biggest example was during the Doge craze during the winter holidays. He jumped on Doge 4 days before any other pool did, then waited to sell until Cryptsy locked up with Doge exchange issues. Hashcows and direct Doge miners couldn't sell on their favored exchange. People were clamoring to buy but couldn't. H20 sold and we made a killing. That's what your 3.88% or so fee goes to. Well worth it.
So don't worry about these high unexchanged values. I love it when they get high, because at the end of the day, we get a bigger payout than if we just autosold everything like all the other multi pools out there during a market downtrend.
BTW- this isn't even close to the highest unexchanged values we've seen.
That's exactly how Middlecoin should remain, crappy website, barely no contact from h2o, and all that. He has better things to do than socializing online; for socializing I bet the man prefers his family and RL friends than noisy, low hash malcontents. Please, please go elsewhere if you don't like this pool, or you like cute graphics or "build communities". Leave more server resources and less stales for the rest of us.