Well their fees are very expensive when compared to the US brokers (even in comparison with their US branch, TD Ameritrade) and from a personal perspective I found their customer service to be really bad. When I moved from UAE to Mexico they demanded a lot of attested documentation couriered to them to 'prove' where I was resident, which I provided at great expense - and then when they had everything they wanted they turned around and said they dont operate accounts for Mexican residents and promptly closed my account.
Interactive Brokers on the other hand have been great.