I use market order only, well kinda. When I click on bid or ask column on DOM, it create a working limit order which is immediately filled at this or better price. So in reality it is market order with the protection not to go over my limit price. I do incur slippage, especially in recent weeks, but my most important goal is to be in a trade should a valid signal appear. Also, if the spread get too big, I will pass the trade even I get signal. Minimizing losses is my main objective. The limit vs market order question depends on your goals and strategy.
I just drill the ask or bid. Max slippage is never more than .25. If I get improvement then that is fine as well.