Smart Product Filter & Search

One of the few apps I can find that allows to filter by metafields using a range (i.e. items with a value between x and y). This is the primary reason that I installed this app.

Front end code is fully customizable in code, which is great, though editing the code prevents you from changing appearance using their app management interface.

Support has been quick to respond to issues that I have had - very happy with the service.