I've been using HF for about 2 years now... Slippage hasn't been an issue with me. Withdrawals are quite faster, just 2 days. More than I can say for my previous brocker AvaTrade which takes about a week.
If you don't violate rules they don't have a reason to delay or reject withdrawals. I would also recommend to send withdrawal request in early morning then it should be processed same day.