Green speed varies by course, and will vary somewhat based on the line of the putt.
Uphill putts have to be hit harder than downhill putts.
If it's windy enough, the wind has to be taken into account too. An uphill putt that is also into the wind needs to be hit harder than an uphill putt with no wind.
On tournament speed greens I use putt stroke strength factors of 0.75 to 1.8. In other words if a putt is10 feet and uphill a lot, I may use a putt strength of 13.5 feet (a factor of 0.75), while on a very downhill 10 foot putt I may use a putt strength of 5.5 feet (a factor of 1.8),
In general, putts hit hard break less than putts hit soft, so uphill putts tend to break quite a bit less than downhill putts do.
Better balls generally offer a slower meter speed.
Meter performance consistency is almost entirely reliant on your computer.
Clear the Flash cache, disable any unneeded applications (particularly any that may be running in the background), and close any unneeded window tabs.
It would be nice if some general green terrain markings could be added to the hole display on the right of the screen.