I did the upgrade and am happy with the result.
The upgrade process itself was not as smooth for me as it should have been, but fortunately there are a lot of very knowledgeable people who post work-arounds for just about any issue that one might encounter. Bear in mind that W-10 has been out for quite a while among volunteer testers and software developers, so a lot of the oddities have been discovered and addressed in some manner, though MS itself has been oddly slow about publicizing fixes.
One thing to consider is that in the default install settings, many of the privacy controls are set to share as much personal information as possible. That maximizes behind-the-scenes potential revenue-generating data gathering, which is what MS is counting on to recoup their investment in putting this all together and boost their profits over time.
One can override these settings during installation by choosing the custom set-up option and picking and choosing what gets shared carefully. Of course, nothing is foolproof, but it can cut down a lot of the marketing “noise” some people have complained about.
B’hatzlacha.