According to the documentation a GET request to /v2/feeds "will return a snapshot of each Xively Feed that is viewable by the authenticated account." When I invoke this service the results include lots of public feeds, but not my own development-mode feeds even though my API Key has access to them. Is that the intended behaviour or am I missing something?
The /v2/products resource provides what I need: I can enumerate my products and then enumerate the devices in each product, but it's not supported by the Xively Java library as far as I can see.
Products and devices are not supported in some libraries. If you want to enumerate all of your feeds (including development mode) the best thing to do is use the feed search API, the documentation for which is here.
What you probably want to do is return all of the feeds attached to your user account. Call this URL api.xively.com/v2/feeds?user=USERNAME.