My thoughts.
I like others I am wary of a 'free' upgrade. If the OS is 'free for the first year', the wording does suggest that it will be an annual renewal fee, a bit like office 365. I have been running the same version of Win7 and Office 2010 since they came out, with no annual renewals.
If it is free it may be that there are still a lot of bugs, but if they want to hit the release date they need to get it out with bugs and all. Speculation, on my part. But again, if there is an annual update fee they still get the money; just later.
Last week MS announced that they will no longer be offering free support for Win7. However, this I think only affects IT departments and the like, not Joe Public.
Vista was not very good.
Win7 was a huge improvement. However, it does not seem to want to support drivers for the new solid state memory drives (super fast and cheap).
XP was also very stable, but won't have the drivers for newer machines.
Also pirated versions of XP is on almost all computers in China. A good reason for MS to want to move on. MS said they were not supporting XP last year and the Chinese government were not happy and promptly banned Win8. Microsoft seems to offer extended support for China, but they deny this.
After years of resisting Apple, I was given an iPad for Xmas. I have had no problems and have spent zero hours on maintenance. I regularly spend about 6-10 hours a month on maintenance for my MS products, and I am only a light home user. That is one day a month of my 8 days a month free time.
I am seriously considering getting an Apple computer next time. Yes they cost more up front, but they will do anything I want to do that MS can do, and even run MS Office files. I think they are not so hot for gaming, but that is not my thing.