I have been using IG-Markets platform since 2008 for trading local (JSE) listed shares via CFDs.
Personally I find the normal online (Via your internet web browser) for trading and seeing market depth not very user friendly. I do all my trades via the L2 Dealer platform which is the desktop version (small program) with live trading and market depth.
I do pay extra for the live market depth data but if I remember correctly you get refunded the monthly fee if you trade more than 3 or 4 times a month.
Overall I have been very happy with them over all these years.
My 2c worth.