Actually Tickmill is quite a good broker. I deposited to my account 2 times 100$ each, and I got my deposits back at least. It is trustworthy, but I wouldn't say that it is suitable for all HFT strategies out there. It is a broker with slippage and requotes. I think it takes about 200 milliseconds for orders to get filled by the server, which is too long basically. Apart from that, spread+ commission are too high as well.