What mapping solution do people use that has a proximity filter? For D6 I used gmap, which allowed me to easily create map-based views and include proximity filters and sorts. With D7 I've been tempted to move to OpenLayers - I like the idea of learning one powerful mapping tool that can be used to solve more problems than presumably gmap could. However I can't for the life of me find anything that looks close to stable for proximity filters and sorts. I find this a bit surprising - does anyone know of anything I've missed? The best lead I've found so far is this sandbox project, but I haven't given it a go yet.

So can anyone recommend a way, with or without OpenLayers, to have Views-based mapping and proximity filters on D7?
As of writing this, jpstrikesback's sandbox: Proximity is really solid. I have it running on a few production sites without issues. Once he feels it's 100% it is either going to be released as the D7 version of OpenLayers Proximity or use the new namespace "Proximity" (as it really does not require OpenLayers to function). 

I recently wrote up a walkthrough of how to get this up and running for another question on stack exchange. See Need a simple Google Maps solution; lost in the labyrinth of modules.

As you mentioned GMap was ok in D6, but using OpenLayers is much more robust and flexible. It's worth spending the extra time to get it set up. Good luck