Hi Anthony,
I did the reverse cruise in mid October '03 on SSS. The weather was wonderful, a bit chilly in Venice. As I remember, Venice was the only crowded city, but I imagine it is like that all year long.
We were disappointed that we could not get to Pompeii, due to a mudslide, but we (Suzanne, Crystal & I) were able to get to the webcam in Sorrento. Hvar is a new port for Radisson, so can't tell you too much about it.
Being a 2 for 1 cruise, I would recommend it.
Can't tell you anything about the Diamond, as our first cruise is in July.
Beth