http://www.spaceflightnow.com/news/n1105/29junosolar/

They should've powered it with an RTG, just like Cassini. The solar
cells on this billion dollar probe will only last three years at the
most, and severly limiting the probe's effectiveness during the mission
when its solar panels aren't viewed towards the sun. NASA and the DOE
have failed to restart plutonium production for RTG's resulting in
maimed and demasculated probes like Juno.

Cassini has now operated for almost 15 years on its nuclear power
source, the Voyagers for almost 35 years. Due to its nuclear power the
craft will be safer since it won't have to rely on batteries during
swingbys behind Saturn. There's a good chance these probes will operate
for quite some time still. Juno OTOH will wear out its solar panels in
a couple of years.

All in all, a waste of time, money and effort in my opinion.