I still have an small account with them, i can tell that the execution is pretty bad. Some weeks they have been very good, then suddenly the spreads increased and execution was a pain... not just for me, was just bad in general from june-august this year (EURUSD) now they are a bit better again. I would never trade with them with big money, my mate had 1$ slippage with a bigegr XAUUSD trade once.... 1$!! For scalping and spread sesitive strategies... be careful. Long term they are better, with small lot you get better prices and swaps are pretty good. It's not that they are the worst, with cashback they are pretty cheap. Some may be happy with them.
Note that i always compare at least 3 brokers with same EA, so most of the time they trade alle the same 1:1, without this kind of testing you may dont notice execution problems at all.