I've only done one in Europe so far - Christmas markets, Nuremburg to Basel on Avalon - which was lovely! My husband wanted Germany, I wanted Christmas markets, longer than 7 days (not enough time) so that fit the bill for us. My in-laws and my mom and her husband ended up coming along with us and everyone but me got sick. Ah well. My in-laws had done several on Uniworld and liked them but they also really enjoyed Avalon (despite being sick). I chose Avalon for the itinerary, fare, and room layout (I love the bed that faces the windows and the "french balcony" which is really just sliding doors.) When I wanted to open the windows, I could (and yes, despite it being December, I did open the windows a couple times!). We liked the company, so we did a Mekong cruise on Avalon and it was even better than Europe ;-)

Honestly, I researched (reviews online) and booked myself - didn't have a travel agent I was using other than booking. I have an agent I use who is more full-service now, but I still honestly only use if/when I'm getting a good deal. I am still researching myself because I know myself and I can always ask questions here, Cruise Critic (despite its problems, it's still the biggest- I joined there in 2006 I think). Tripadvisor or other sites for general tourism things.

From reading CC for so long and seeing how many companies respond to problems (used to be low/high water problems, now it's the pandemic) I probably wouldn't cruise Viking (too many people on the boats for starters ;-) I love that there are more specialty cruises now, and more activities available for excursions, like biking, ebikes, hiking (with bikes and poles available to checkout on many boats - check if that's something you'd be interested in!) or wine cruises, cruises with writers, musicians etc - I follow a few companies on social media and see the adverts and they look fun! Hubs wants to do a spring cruise through Netherlands for flowers, Rhine Valley for castles earlier in the season when it's daytime, and I'd like to do a Christmas markets cruise again and see Vienna and Budapest. I wouldn't mind doing the "full transit" - my in-laws did Amsterdam to Bucharest - enjoyed it, though they weren't as impressed in the areas where there wasn't much of a tourist infrastructure developed yet. That was a decade ago so perhaps it's different now. Or perhaps - like me- you prefer the less traveled spots too! Anyway, I highly recommend Avalon if it suits your needs, and I'd try uniworld (though the decor is over the top for me ;-) or AMA or...there's one other I'm forgetting. Tauck, Scenic?