Am running my Pi with ownCloud and a 1Tb ext USB drive.
Pretty easy to setup. Downloaded a ready made ownCloud image, and using dlinkddns to update ip address. Have a BT hub 5 which is easy to setup when you know which settings to change.
I am using ownCloud clients on our home PC's and on the boys PC's at Uni, and all works very nicely, if a bit slow.
Has been running 24/7 for 2 weeks now with no problems, seems pretty reliable so far.
Anyone else using ownCloud ? how are you getting on with it, speed, reliability etc. ?