It had been so long since I had watched it that I had forgotten some of the surprises. I also think that I missed a few episodes near the end when it originally aired. So it was still reasonably fresh for me despite knowing the entire plot, how it ended, and some of the surprises.
Still a great show to watch even though I recalled most of it going into it.
That being said, now that I have watched it again, I'd probably have to wait another 15 to 20 years before watching it again for it to be as good.