They report a maximum of 16.2nW, open-circuit voltage of 899mV, short-circuit of 107.4nA. To give hackers a reference, in its current state, you'd need something like 50,000 of them to power a single 0.85mW Arduino chip.
In the U of Missouri article they say "The radioisotope battery can provide power density that is six orders of magnitude higher than chemical batteries", but as far as I can see from the article they're not talking about their own battery; it's a general statement quoted from an old paper (F.K.Manasse,J.J.Pinajian,and A.N.Tse, IEEETrans.Nucl.Sci. 23,8601976).
The article in question is "Radioisotope microbattery based on liquid semiconductor" (Applied Physics Letters 95).
"[beta batteries can be] Paired with chemical batteries for high current, limited duty cycle applications BetaBatteriesTM increase shelf life and ensure readiness by acting as a trickle charger, thus enhancing capability, reliability and useful life."
In other words this dime sized battery probably doesn't have enough current to power electronics continuously w/o some help.
Does that help?
http://munews.missouri.edu/news-releases/2009/1007-mu-resear...
It references a published paper (likely behind a pay wall), otherwise the content is almost identical to the original link.