So I took the 'plunge' and signed up to Oddsmonkey a couple of days ago. Great site, really professional looking and absolutely foolproof to get into (over 100 tutorials and excellent software which basically does all the number-crunching for you).
Already £33 profit, although word of warning; for any profits above, say £15 per bet, you need a heap of liability (one bet required over £80) on your exchange site (betfair, BetDAQ, etc), so make sure you have a decent amount of starting capital.
I'm posting this as somebody who had next to no idea how betting works. I've maybe placed about 5 bets in my whole life before this, just to give anybody interested but a bit hesitant about betting an idea of how easy it is.
Word of warning part deux: It's addictive af
Edit: There's a free option on Oddsmonkey which grants you access to the basic tutorials but your profits are limited to £45, and you don't (I think) get access to their tools such as the Oddsmatcher and calculator. £17.99 per month gets you premium membership and you'll make that back after your first handful of bets easily.