I've had a 2010 LR2 for about 8 months or so. I definitely don't get 20 mpg average. In mostly city driving I get around 15, sometimes lower. On a recent roadtrip I got 20-22 highway @ 75mph with premium fuel.
So far I haven't had any major problems. On the way to my first oil change, the tire pressure monitoring fault alarm came on. They replaced the sensor no problem. Not sure what triggered it.
I've read that the 2008-2009 versions may have rear differential failures. Supposedly there is a "redesigned part" but no recall, which may signal they know about the issue. If it fails outside of warranty it will be pricey ($5000+). Check out this forum:
http://www.landroversonly.com/forums...failure-41070/
Knock on wood I've had no problems and love my LR2. If you could pony up for a used 2010 I would for peace of mind.