I have kept a record and I am seeing returns of anything from 3% up to 10% of my back bet. On only one occasion did I chicken out cos I thought the price was going to go against me, but even then I made a small return. So, of the 20+ bets I have placed, I have yet to lose on any. Yesterdays was a good one - backed at 1.7 (reduced to 1.44 cos of NR), but still trade out at 1.29 for over 10% ROI.
Because the odds are less then evens I tend to lay for equal profit as there isnt much to more to be gained from underlaying at these prices.