FXCM has introduced “At Best” Order Selection
This feature enables you to have market orders filled during fast-moving markets. Orders are executed at the best rate that is streamed to FXCM from multiple banks and financial institutions.
since Quotes are from multiple banks and financial institutions. You can have “At Best” quotes during News.

is it “At Best” for bank and financial institutions. ?
and “At Worst” for Trader. since selection of "At best" can make your order fill to “At Worst” price since you are allowing them to fill order at next best available price, which is always worst, you will never get fill which is lower than your price..since that is taken by broker and sold to you at your price.
If you click sell GBP/USD at rate 1.9782, and if price fall just 1pip at the time you click button , you will get price moved. or order will wait for
some second and if price further drop. your order is rejected.
But if the case is reverse..your sell order will get fill immediatly at price you clicked, even price has gone above 2pips, but they will never never execute orders in your faviour.

so think carefully what is "At Best" order or is it "At

"
Pl share your experiance about "At Best" type orders, it may be good experiance. i have shared my first imprssion about at best order. I may be completly wrong.