Sorry for the delay, been out of the office.....
Not an easy question (which is perhaps why you and I are the only two here at the moment?).....
Lets look at the one, iron clad, rock solid, must have feature that groov needs.... SVG, scalable vector graphics.
If you are going to use groov, your browser must support this feature. It is this feature that cuts off IE 8 and older.
I love the caniuse.com website for its clear way of showing what works in what.
So, here is SVG; http://caniuse.com/#search=svg
Please take a moment to review all the sections.
As you can see, we do have some greens, so we have some support for this critical feature.
If you can install Firefox or Chrome on a Linux install, you should be good there as well.
Note they do not have any WinCE browsers listed. (Google 'wince svg' and see how much support it has).
Lets take another example, CSS, groov uses that and needs it.
Again, some green, but, then there is some solid red as well.... Including Edge, which you said you found worked well.
Clearly, groov, at this point in time, does not use the 'CSS all property' function, if it did, Edge support would break.
What we need to do then is to carefully balance the features of groov with the bulk of the browsers compatibility. Not an easy line to walk.
And that's the main point, depending on gadgets you use on each page it will change how well that page will render on the browser you are using, on the device you are using it on.
So, in the docs we simply state, to use groov you need to use a modern browser.
We have thought about doing a bit of an open source matrix so people can fill in their findings. The shear number of browsers and platforms is impossible to test all groov gadgets against. Crowd sourcing our QA is not something we expected to consider, but we also cant purchase every device that has a web browser either.
I know, not the answer you wanted to hear. There are a lot of variables. A. Lot.