Glenn Vanderburg likes Seaside and Rails:
But there's a funny thing about pain: when your worst pain goes away, it doesn't take long to start being annoyed by the next worst. So it won't be all that long before Seaside's particular strengths start to look really attractive to developers who've grown accustomed to Rails' niceties. And then it'll be time for Seaside (or possibly some other continuation-based web framework inspired by it) to get the buzz again.
There are things Rails can learn from Seaside, certainly, but there are also thing Seaside can learn from Rails, and that learning will probably happen in both directions. As Avi pointed out in another blog this week, Smalltalk and Ruby are much more similar than they are different, so I see the two frameworks complementing (and, as above, complimenting) each other for some time to come.
The main thing is, more and more people are seeing that the roads taken by Java and C# are the wrong ones.