I've a NIBE fighter (1120, I think) and am very happy with it. It sits in the shed and I basically ignore it! The one thing I would say is that it doesn't have any timer functions - I'd like to be able to just heat the day's water on nightrate electricity, but it doesn't allow that.
Running costs for all heat and hot water of about 1200 a year (based on 200 sqm house, working from home, total electric cost of 2000 a year).
edit: what collector bed are you considering? The one problem I have is that I have a small glycol leak somewhere in the collector bed so it eats about 5 litres of glycol a year). Getting the right people to do the assessment and installation is at least as important as the equipment itself, IMO.