I'd been with Oanda since late 2005.
For the majority of the time I considered them the very best Fx broker.
Early this year I made the move away from Oanda to TD Ameritrade (thinkorswim).
Oanda spreads do widen drastically whereas TDA typically includes a fixed spread 2.5 points.
Because I really don't own scalp, I do not believe this a large cost difference as TDA's platform is literally exceptional. Oanda's is decent but leaves a lot to be desired.