The one thing I find useful about the matrix is moving orders.
I trade short term intraday and sometimes I want to move orders slightly. For example, I may have a limit order in to take profits on a trade and find that the price just isn't hitting the mark, so I can very quickly click and move the order to a new position, much faster than the order bar. Or, it could be the opposite and I feel that the price is reaching my limit on momentum and I would rather take any extra profit I can get. Again click and slide easily and quickly.
For trailing stops, this too can be very handy (The next version of the platform due out any day now should have trailing stops in the order bar, both dollar and %).
Though when trading, I use the matrix, two order bars and hot keys oh yes, and the 'market order' entry on the matrix as well - I just use the best tool for the job I need to do at that exact time.
And if nothing else, seeing a great big block of red in the P&L column on the matrix in a loosing trade, really drives home the psychological aspect and makes you cut your looses short as well
It's a horrible deep blood red colour