so here is the deal: it attracted me that they had the lowest spreads....hands down lowest spreads amongst all SB companies...and in the beginning all was rosy. something changed along the way, and when I tried to deal with them I never got the price I really wanted to, or saw on the screen. So I stopped trading with them....I am sure there are some who got good experiences with them, I am just not one of them.....
I use CMC quite happily, but i would advise the following.
Always have your blotter open.
If you think you have carried out a trade but it does not appear in the blotter log out and log in again.
Always have an "emergency" stop loss in place for when the system goes down (not very often but I hate being in a position and not being able to control it.)
Always check your statement.
I've been using CMC for a couple of years and the only actual problems I've had are 2 trades wrongly charged to my account, both corrected to my satisfaction and none in the last 12 months.