yep I'am still in the process of improving gTile for cinnamon.
latest changes include full support for the different panel positions (top, bottom, both) of cinnamon for grid and auto-tile.
For what would the pull request be good? is this the way to get the extension listed on http://cinnamon-spices.linuxmint.com/extensions
I consider gTile to be very stable, the only difference to the gnome3 version may be a panel icon (dont have a gnome3, but the code looks like there should be one...) This is the next thing which I'll look into. And I'll also test the multimonitor support.
Would be a great thing to see gTile on the extension page