I'll recommend Betfair anyday over the others. Betfair with its...

I'll recommend Betfair anyday over the others. Betfair with its increase in commissions is also get irritating but it's stll better than the others. Being an exchange you get the best price and there is a fair amount of liquidity.

Don't be put off by the interface; it's very easy to use and software like Bet Angel and Geeks Toy make it much easier. Bet Angel is costlier but has automation which means you don't have to sit by your PC.

I only use these corporate bookies for quaddies and Hong Kong (Betfair does not do Hong Kong or exotics, AFAIK).