We hesitated a long time also, and like you have no use for MU, and just went from 5.029 to 6.1.2. It went easily (aside from the IT staff mistakingly installing 6.1.0 first). The prescription writer is somewhat better, still some imperfections (doesn't remember pharmacy yet, not displaying Rx instructions as well). Otherwise, it was pretty invisible. It is no slower than 5.029. A version 6.2 has been mentioned that will address the forgetful pharmacy issue.
We changed to get a little better action out of the prescription writer mostly. Mail in pharmacies show up quite a bit more easily. We are not doing health maintenance or order reconciling, so changes there are invisible to us. There was also the issue that even if you keep the prior release static, other things change around it, like OS upgrades. Any software company will be devoting its efforts to making sure its current version works with those changes, and little effort towards its legacy products. Pretty soon, the corporate memory for the older product starts to fade, and support becomes less reliable. We called with some issue on 5.029 maybe 3 months ago, and got the response "You REALLY need to upgrade to a more current version..." This last week I had the dubious pleasure of investing $3,000 in upgrades to our other databases because the older version will not run on any current production machine, and sooner or later one of the servers is going to break. I guess I did not want to worry about coming in on a Monday and finding the whole system down with no quick fix at hand.
As to just when? Well, that is a bit like forever waiting for the next version of your favorite computer to come out because you know it will be faster, better and cheaper. I would base your timing on when would be the most convenient time; a long weekend, maybe. All versions will have some imperfections, and the next better version always just a few months away..
