I have used them as well. Great service and telephone support.
I used the "private traveller" where it is not possible to choose the seat in the booking, but they will give you one. When I got my Amadeus number in the confirmation, i checked my travel on checkmytrip and found that my favorite seat was open. I called them and they changed it without trouble. The feature I like is that you can pay by banktransfer, but that is not possible on "business traveller". Travelling back from EWR I was going with a friend, but I did not know his seat at the time of booking. I was told to call them back and they would try to help me being seated next to him if possible (they could not change his seat, because he had used another agent with another system, btw. that internetagent did nothing to help him).
I will for sure use them again, but next time maybe as a "business traveller"