I have good time on my Rad/Rad.
The early levels are kinda slow and boring... but once you get into the upper teens (cosmic blast--18 I think) things start to improve dramatically. Get the two single targets (neutrino bolt and x-ray beam) since it will also help make things move quicker.
However, Rad/Rad for me is the most fun in groups with all the aoe abilities, debuffs from both nukes and toggles, AM buff, rezzes, exploding bodies.... very fun in group.
Another note, is that it isn't too hard or too expensive to get haste/am "permanent." However, this weekend prices seem to be higher due to the double xp weekend.
Crime of Fashion has a lovely guide, once the guide links are functional, I suggest you give it a read.
Good Luck and Have Fun! 
Fun for me started at 20+ with stamina... due to the cone and PBAoE attacks, along with toggles, unless you delay some of them, it will drain your end horrifically.
Some of Radiation Blast's attacks might feel a little sluggish and slow to affect enemies (like Neutron Bomb, despite how awesome it looks), but even so, it seems to go well with Radiation Emission. You might want to look into getting Achilles' Heel procs in some attacks to further reduce enemy resistance. 
Ideon's Paragonwiki page
Member of Paragon/Rogue Knights
Arc: 60092 - Supa Rumble in the Park
"Keep living the dream, and never let any jerk tell you what to do."
-- High-Roller
I have made a Rad/Rad and i am currently lvl 10 can anyone tell me if it gets anymore exciteing to play been pretty boreing so far sticken with it cuz i love the concept.