I am just going to add a little more, by suggesting that Ultimaker have done a fantastic job with both the development of their software, their hardware and importantly this community. If you are using the 3D printer for hobby projects with normal use, then all of the problems mentioned above will happen yes, but with a little TLC and patience you can get the UM2 working flawlessly.
I may just be a lucky one, but even though I read everywhere about feeder issues, underextrusion, adhesion problems bla bla bla, so far my UM2 is doing a great job! I am using NO modifications to feeder systems or extruders. Yes there are a few tricks that I have learnt along they way, this community is priceless. But honestly, I think the UM2 kicks ass on the competition at the moment!
Loves ya x