It's about time. The old fractional system is confusing and outdated.
Decimal is much easier to work with since you simply multiply your stake by the odds to give your total return (which is why you add 1 when converting, to account for your stake in the calculation). No need for long-winded calculations to work out how much you win.
The punter would soon realise it is much simpler - £5 at odds of 4.1 = £20.50 total return. Accumulators? Multiply all the odds and the stake together. Easy.
As for squeezing prices, if bookies work out a price is 2.16 decimal, which fractional odds are they more likely to offer - 11/10 or 6/5. The lower obviously giving you less value. I'd argue that decimal would give punters more accurate odds.
I also know a bookie/odds-compiler who works for SportingBet and I agree with what he says on this too:
Britain is the only country that uses this pounds shilling and pence antiquated system of prices. The vast majority of punters in this country under 30 use decimals as standard now anyway. The biggest betting site in the UK Betfair has never used anything but decimals. Theres very few prices that don't neatly convert to decimals. Very little will change at all in terms of margin, and some will work in the punters favour. 15/8 becomes 2.9 for example and 13/8 becomes 2.65. Won't stop the paranoid punter from moaning that the bookmaker is cheating him though, because nothing ever does.