I'm 50 miles into a new blend with no problems, light, or warnings so far.
I put in 7.5 gallons of E85 with 6 gallons of E10 and I had 1.5 gallons of plain 'ol gas left in the bottom when I started.

Assuming the E85 is actually 85% ethanol, this = a 46.5% ethanol mix.
Assuming the E85 was really 70% ethanol ( minimum allowed in winter ) this comes out to be a 39.0% mix.

So without testing I can say I have at least 39% and at most 46.5%.

Following my Long-term fuel trim with a ScanGauge:
E45? runs about +14% at 65 miles per hour.
E30 runs about +8% at 65 miles per hour.
E10 runs about +3.5% at 65 miles per hour.

Per a 2004 ed. Ford manual (for MY2005), a MIL lamp trips if LTFT > 25%. ( +/- )
Per a 2006 ed. Ford manual (for MY2007), a MIL lamp trips if LTFT > 28%. ( +/- )
Per a 2007 ed. Ford manual (for MY2008), a MIL lamp trips if LTFT > 29% or -33%.

The E85 was $2.229 and the E10 was $2.869.
The blended tank cost $2.549 which is a 11.2% discount.