Selling asap is not always the best choice, so manual trading should be kept as an option.
For example, a coin may be going up in price but profitability may be going down instead, because of difficulty or block reward.
Personally, I think manual trades are what makes middlecoin what it is.
Sorry if I often name MC but it's the de-facto benchmark for btc multipools and I'd really like to have an option to them, this be clevermining would be fine :-)
While that may be true, there is also the possibility that the coin drops in value. Auto trading almost promises the current value, so the system can switch to that coin. Keeping the coins delays payouts, and has a probability of Terk having to pay using his own money.
My guess is that in the long run, best profitability would come from selling the currently most profitable alt (what you are mining at the time) for btc as close to as soon as you mine it as possible (taking into account appropriate batching to minimize fees) - UNLESS there is a long enough, unavoidable delay in being able to transfer and execute those sales. "Long enough" in this case being relative to the exchange rate volatility. In that case, if the delay is unavoidably long, then using some judgement (say in the case of a sudden, rapid and unexplained drop in value of alts you just mined and haven't yet exchanged) would probably yield better results than a slow, automatic system.