Gnarkley, one aspect of Betfair you might want to consider are their fluctuating prices.

The prices are recorded somewhere on their site but these are the prices at, or just after each race. However, it is my understanding that they do not show the highest and lowest traded prices. If this is available it might be intriguing to look at them.

When comparing Betfair prices with other betting agencies/features it might appear that Betfair prices may not be really competitive as would be hoped. This might not necessarily be the true picture, especially if the price firms at the death. This could be also true with Best Fluctuation but my Betfair experience shows that B.Fluc tends to firm at a greater rate percentage-wise than Betfair.

There have been numerous occassions, even 30 seconds or thereabouts before a race when I've had a bet, only to see the price move dramatically.