Have been using Mirago for a couple of years and yes it doesn't generate too many click throughs...but in my area Mirago has the cheapest cost per conversion which makes it still worth using.
This months figures for me are...
Cost per Conversion, #Conversions this month
Google £24.31, 130
Overture £15.14, 88
Espotting £12.67, 19
Mirago £4.47, 7
To add to this thread...so long as the cost per conversion comes in at the right price and there are enough conversions to merit running the PPC account..then I'll sign up with any PPC.