Mixture along with several other posters here are slightly missing the point with "beta" / service pack comments. The "release" is a bit of an amorphous thing / grey area...
Back in the day we had "gold master" / RTM. That was ostensibly production-ready code, but of course you could wait until SP1.
In this brave new world, much has changed. We have "RTM", but this is still not actually production-ready. The RTM is more like RTD - release to developers. The actual "release" is called GA - general availability. There can and will be many, many patches of the RTM OS between then and GA.
Also, Windows is now being developed by what used to be the Windows Phone team (led by Terry Myerson), who have a history of releasing incomplete software and then updating it.
And then, if you're waiting for SP1, you're out of luck. Win 10
will be updated like Ubuntu, with three branches:
- Consumer branch (latest stuff, every 4-6 weeks)
- "Current branch for business" - same as Consumer branch but delayed a bit
- LTS, which is similar to the conventional model of Windows releases, in that there is a new release in an "appropriate time frame" - probably somewhere between every one to three years, that is supported for 5 years, but doesn't receive new features.
You can skip one of these releases, and still be supported.
So, if you really hate change, and want a stable product, probably the best thing to do is to wait until the second LTS release.
Personally, I'm going to jump on the "current branch for business" about 6mo after release.