If you care about REST (and arguably you should) then URLs are not an implementation detail. Especially if you are creating an API that others may eventually use to get at your data, URLs are everything. I'll say it again: the application is the URLs. Because ultimately the application is its resources and simple manipulations of them, which the URLs are representing.
Caring about what URLs look like is at best irrelevant, but normally extremely counterproductive to actual RESTful implementation. If you're building URL strings to make requests (save for get-based forms) anywhere in any of your clients, you're doing it wrong. Wanking about pretty URLs just encourages you to go in the wrong direction.
In true REST, URLs are opaque identifiers. They might as well be UUIDs. The only way you're supposed to get one to request is in a response from the server.
Hypertext. Is. The. Engine. Of. Application. State.
