My wife and I spent six days on the Cloud from Tenerife to Barcelona in April 2010. By way of background, we were originally supposed to be sailing on the Shadow in the Caribbean but rearranged at the last minute due to the volcanic ash leading to our flight being cancelled so we hadn't particularly researched the specific ship or itinerary.
We are in our early 30s (so much younger than the Silversea average) and this was our first time on Silversea so I can't comment on whether standards have slipped etc.
Overall, we had an excellent time and would recommend this line/ ship to anyone. Sure, there were a few minor niggles, but nothing that would affect our decision to sail Silversea again. The only major negative was a mix up with the booking (due to our late change onto the cruise) such that there was real confusion when we arrived so that they thought we weren't even booked on the ship and then they couldn't find our cabin, but this was resolved quickly and efficiently (although our cards showed us as US and not UK citizens!) and isn't entirely surprising given the large number of changes the volcanic ash must have caused.