What would you like to know? I current trade for a trading firm, but I try to be unprofessional as possible ;-)
I'm sure they all work differently, but my experience is based on a profit share arrangement. If you think you are any good, then it makes sense to work in a arrangement where you back yourself and your abilities.
All in all, I have found the experience so far to be very positive. There are some restrictions obviously, and I had to modify my trading somewhat to work with in the parameters, but it has made me think about my trading more and that has had a positive flow on effect.
It's also nice to interact with people with the same "day job". It's also good to bounce things off other traders.
Like all things in life, I am sure some companies are better than others. From what I can tell, I'm lucky my first time out is with one of the better ones.
