I had one for a year not so long ago, before I got the Fazer bug (again). I bought mine, a 12 plate, with pretty low miles (about 8k on the clocks I think) and did around 4-5k on it in the year I had it. At that age you'd expect it not to have any reliability issues (and it didn't). It was reasonably brisk, capable of handling autobahns without a struggle, and supremely comfortable. Pretty neutral handling, no surprises anywhere. All round not very glamorous but a damn good workhorse.... these are the kind of bikes that are scorned by those that don't know them but well rated by their owners generally. And much more popular in Europe than here where they never really caught on. Whilst the 850's are pretty agricultural the 900's do have a little more finesse about them.
I do know the 850's are very sensitive to oil levels - not sure that's the case with 900's though. There is a good community online - look for Carpe TDM. All you need to know is there.