The big problem for me is SPEED. I think we here know very subjectively the KDE3.5 flies and KDE4 seems to crawl. There was a very interesting discussion by Zack Rusin on QT drawing performance: http://zrusin.blogspot.com/2009/08/2d-in-kde.html
Solving this problem in a network aware and hardware accelerated way on all cards, will make a massive difference to KDE4 perception.
Did you read the followup post to that? It looks like the difference is not as big as it seems, and it has many drawbacks.
http://zrusin.blogspot.com/2009/08/more-2d-in-kde.html
For me Plasmoids are not vastly useful. I prefer apps in windows to apps on desktops.
I agree!
To be honest I think if Kicker was ported to KDE4 then a lot of people might be won over. Or a Plasma-lite option.
This was discussed, but nobody came forward to do it. Therefore the community has resorted to filing feature requests on Plasma for kicker-like functions.