Talking 10%. It's not going to be enough to cause major problems, nothing that taking care of the fuel system will not prevent. Fuel filter changes will help a hell of a lot as well.
Diesel cars are running up to 20% Biofuel mixes without any problems.
Honestly, I wouldn't worry about such a small amount of ethanol in the fuel, it's when you get to the bigger numbers like E50-E80 that the problems will start.
Spot on on this. 10% won't be noticeable really, only on a dyno. In Brazil they run E100 for the pure Ethanol, then the gasoline is mixed with an E25 blend. Pretty much all cars there can run on either one. For example, my dad has a Peugeot 307 SW. It has the typical 55l tank, then a smaller, 1l tank for gasoline in the engine bay.
The 1l tank HAS to have gasoline for initial start up (a car running E100 will struggle to start from cold), but it switches to Ethanol as soon as it's running, that 1l deposit lasts about 2 or 3 months.
It is recommended that you run a full tank of gasoline every month to lubricate the system, but my dad has been running Ethanol (with the gasonile tank on a monthly basis) for 3 years no problem.
What are the advantages? Ethanol produces more mid and top end power, increases the HP by a healthy figure. It is also very cheap, about half of the price of gasoline.
Disadvantages? Where as you may get 250-350 miles from a full tank of gasoline, you get about 150 miles MAX from a full tank of Ethanol.
A mixture of E10 here in the UK won't affect anything, it might bring the cost of petrol down a bit too as it's diluted with cheaper stuff (the Ethanol). As Agreeable slick said, maintaining a good fuel system with frequent fuel filter changes means you won't really notice the E10, and neither will your engine.
