Session has been updated several times over the past year (all for free), and works well inside DP as a plug-in and as a stand alone sound module. Its UI is a bit weak (with that odd mixer redraw) but hey, its purpose is to produce sound and this it does very well. Osmosis works well for importing sound libraries, and if you want to get "under-the-hood" in sound manipulation, there is no other soft-sampler with the flexibility of Unity Session.