Worst: F***Page (enough said! Thank goodness they're finally putting it out of its misery) although Internet Explorer (especially if we're talking printing) comes pretty close.
Best: SQL Server 2000. Solid as a rock. (Boy have they screwed up management with the sloooooooow Management Studio replacement for Enterprise Manager).
Sadly, I think most Microsoft products rate as "poor" as in buggy as hell or "How the hell did this get past QA?". These days the answer seems to be "Let's not worry about shipping one product. We'll ship endless dribs and drabs over the internet as and when
we finish testing them". A step backwards in my view and a nightmare to control and keep track of.
And I still don't understand how you can have a "market leader" product used by millions all over the world that can't even count the number of pages in a document properly (How often have you seen "Page 95 of 93" in a Word document footer!) or can seemingly
at random print a big red cross where the image in the document shown on screen should be?