Well I can't wait to hear your impressions. On our cruises to date we haven't had a problem with the fixed seating, only because we've either been with our kids and we got our own table for 4, or, in the case of our Alaska cruise on Celebrity, we were assigned to a table with two other couples who turned out to be just the most delightful people you could hope to meet, and we spent much of the cruise hanging out with them. But I realize that was just a stroke of luck, and it could easily go the other way. I imagine I'd be a little irked if we met some other people and would have liked to dine with them, and couldn't. That does seem rather restrictive!
I will say I didn't particularly like the idea that we had to eat at the same time every night, and I'm looking forward to not having to deal with that.