Yes, I've had an IG index account for the last few years and I've also tried a number of other SB frims.
I've got an account with barclays and also I've had a good look at my father's IB account.
Key differences between abn amro marketindex and the SB firms Ive used (IG, tradindex among others)
AA Bank vs Bookies
pays 4.5% interest vs nothing
positions taken in units/lots rather than £/point
prices reflecting actual market prices vs occasionaly very dubious prices ('Transparent pricing, fully automated trading from market making through to trade execution. ')
Market hours reflect futures markets rather than arbitrary times
They seem to win plenty of CFD broker awards so that's good enough for me. Either way I couldnt care less if they consistent of two blokes in a bangalore call centre as long as I get accurate prices and quick executions (I've never had to wait more than few seconds)