Ok, I experimented a bit further with this package. It seems as if it has some major drawbacks: Since it adds another key to each document (containing the subscription ID), the server has to send a
change message for each and every document once the subscription changes. This seems to be necessary for the mechanism to work, but it causes significantly more network traffic, especially if you have a lot of documents like in my location-based app where documents are displayed on a map.
Also, I noticed that if there are two scoped subs referring to the same collection and you modify the parameters of one of these subs, a “flash of content” appears in the other subs. I haven’t found out yet why this happens, but it seems as if the other subs have to rerun because they have to decide whether their documents are included in the scope again. In my map app, for instance, I have two subs on the same page: one that shows pins on a map, based on the map section displayed. The other is a feed of the recent pins that have been dropped. Even if on the map only one pin is visible (high zoom level) and I move the map a bit (which normally would cause no changes), the other sub (with the feed) updates all of its documents and flashes for a short time period.
I think I have to revert back to using manual queries to separate the subs, although this is pretty cumbersome if you have complex queries that then have to run on both server and client-side to sort things out.
But thanks again for pointing me to this package.