Thanks Boxy. We like cruises, but I was thinking that if it was raining while you were on board, the river boats don't look big enough to have a lot of entertainment on them. I think the Rhine cruises look fab. They also seem quite expensive compared to sea cruises.
the trick is to go in summer. It is difficult predicting the weather in Europe these days but it's generally more settled than here. River boats tend to be much smaller than ocean cruisers (they have to fit through locks and under bridges), so they don't have the same scale of entertainment, though I think one or two have pools. It's more about relaxing and enjoying the scenery. Most cabins have balconies, though they're often more like French windows without room to actually sit on them.
you should aim to pay a lot less than the brochure price, the lines are always discoutning. Get yourself on the email list of someone like Viking and they'll let you know when they're offereing special deals (in their case it's usually earlier rather than later.
Sign up top right corner. There are lots of lines, some cheaper and some dearer, but I've enjoyed Viking. I'm pretty sure they're already selling 2015.
River cruises don't need the vast amount of entertainment than ocean liners do, because they don't spend days and days with no outlook except acres of empty ocean - there's always something to see on a river cruise.