I bought one a few weeks ago to replace my Escort runaround... currently getting 28.5mpg according to the computer, sitting on the motorway at 70 (

ish) will return about 35mpg constant.
Mines pretty stock, stainless backboxes, k&n panel filter in stock airbox... goes pretty well considering its fookin heavy (c1500kg I think) and I popped off the resonator snorkel from the side of the airbox the other day and the sound on WOT from 2500-4000 is awesome.
I came from a Subaru that did 180miles average to a tank, was looking at spending reasonable money straight after I sold the Impreza on something like a Focus RS because I was desperate to save myself driving the Escort more than was absolutely needed.. but saw this ST200 for reasonable money and went for it... now I'm in absolutely no rush to find a 'good' car, its been a complete surprise.
What I would say is that if you're expecting it to be a lazy, punchy V6 drive then you'll be let down.. you really need to wind it up to get the best from it, IIRC peak torque is just over 5k rpm, but once up there its easy to keep on the boil and actually handles pretty well.
Cheers,
Grant