I'm sampling KDE Trinity right now, because I don't like the KDE 4 desktop but recently learned about Trinity as an alternative that maintains the look and feel of KDE 3.5.
I like Trinity. It obviously is indeed a continuation of 3.5, with the slight changes in appearance that you would expect from an updated version. I'm not going to do more than sample it yet, because apt-get (using Synaptic) won't let me uninstall unneeded Trinity software (toys, screensavers, etc.) without uninstalling the core, and I take that to mean the packages need more work.
I don't really know what to say about it technically (and if I knew, I probably wouldn't understand what I was trying to say); but clearly, if you don't like KDE 4 (and/or you just had no interest in abandoning KDE 3.5 for any other desktop software--that's me), Trinity is the future.