I cruised with a group of runners, and that part of the cruise was fantastic. Our group was well taken-care-of, from start to finish. Our group breakfasts (private buffet) were FANTASTIC!
That said, there were some odd issues I have not seen before on Royal Caribbean. The dining room service was mediocre at best. Very poor bar service in the dining room--you were better off getting your own drink and bringing it in. I LOVE breakfast in the dining room most of the time, but on Radiance it was indifferent. Poor service and barely adequate food. I'm not a foodie, not really fussy at all, but if you requested something specific, you weren't going to get it.
Some of the shows and entertainment were fun, but there was one truly terrible show (Piano Man), and one duo that was pretty awful. The Piano Man show made no sense--it was like they all decided which songs they wanted to sing and then tried to find a theme to unify them--totally did not work. Also, it would have been better if the main female singer was not singing flat--ouch!
Not sure of the category, but our cabin steward Fajar was awesome! He knew our names within 12 hours, and as soon as I requested ice, he filled the bucket routinely every day.
The cabin itself was cozy and comfortable--I would choose it again.