Just got back from the 7/12 - 7/20 Mariner Baltic & Russia cruise. I'll post notes on the cities visited on the destinations board. These are notes about the Mariner.
We sailed on her last July in Alaska, a few months after she was launched. Last year the service (dining room, room service, ect.) was spotty due I'm sure to the fact it was a new ship, and a much larger ship than Radisson had experience with. What a difference a year makes. The service was well polished. We also saw a lot of crew and staff from our Alaska cruise. That is a good sign as too much turnover keeps you from achieving that polished state.
Avoid room 937. I chose this room cause it was against a firewall so you get total balcony privacy on one side. The problem is there is a pipe chase along that wall so we heard almost constant, water draining from the tub, sinks and toilets of the rooms above us. It was not loud, but at night when all was quiet you could really hear it. I wear ear plugs to sleep or I would have asked to move. I'm guessing all the rooms against the firewall are likely like this.
We really enjoyed the cruise. We will continue to leave the Mariner very high on our list of choices. After talking to lots of people that really liked the smaller Navagator, I think we will try it in the future.