Doktor Avalanche
Windows 8.1/10 seems to handle multiprocessing better than Windows 7. 
But the huge reason is it's a free support upgrade. Windows is only supported for a finite lifespan, and you will find people will eventually stop developing for Windows 7, probably sooner than you think. 
If you are clever you will upgrade before you have to pay for it (around 11 months time), and wait at least until next year for the bugs to die down and driver support to be improved. Before you do it make sure you back up though.
 

bitSync,
These are wise words from the Dr and the other posters.  IMHO if you are running Win7 on your DAW machine it is best to wait a while for the "Post Release Beta Testing" to be carried out on Win10; I will continue with 7 for now.  A free upgrade from Win8.1 to 10 makes sense since most, but not all, of the improvements in 10 were intended to tidy up issues with 8.1, especially the interface. There is probably much more benefit to be gained in upgrading some other aspects of your DAW, such as installing an SSD if you haven't already.
 
I have read that Microsoft is having trouble persuading their Business Customers to upgrade to 8.1/10 so it is likely going to be several years before 7 is unsupported.   Regarding waiting time, it is important to put the cost into perspective, if you miss the free period you are going to be out about $100 which is a lot to some, and not much to others.
 
BTW, I am using Win 10 on my touch screen netbook and have relearned an old lesson.  The excitement of a new piece of software wears off after about a month.  As others have noted; Reliability is king for a DAW and the excitement remains in making music.
 
Cheers.
 
 

Thanks all for your thoughtful replies.  I don't use touchscreen, I'm more of a tactile surface kinda guy, so no touchscreen incentive there.  I'm a little concerned about some drivers, especially for the no longer supported Frontier Tranzport (I'd be interested to hear if anybody's using that successfully in Sonar Platinum under Windows 10).  For now I think I'll let my brave Sonar brethren put Windows 10 through the paces.  I believe Windows 7 will be around for quite a few years, so I think I'll be OK parked on Windows 7 for a while, so long as Sonar remains compatible with the OS.  This has been a really helpful thread for me.  I really appreciate all your feedback!

I'd say if none of these interest you, don't upgrade.
 
Evolved start menu - desktop friendly
Action Center
Snap assist
Multiple desktops
MS Edge browser
Universal Apps
File Explorer improved
Continuum
Windows Hello
Cortana
Direct X 12
MKV and FLAC support
improved storage management
improved Universal App performance
improved battery performance
Midi and Audio bugs fixed
Low Latency audio coming to WASAPI/ WDM (Threshold 2)

Nice summary, SoundTweaker.

I upgraded 2 laptops and a test Desktop from Windows 7 to Windows 10, they are all back on Windows 7. I just don't like it at all. the looks are enough to make me make the switch back, hideous. Someone up top said that it looked or was more like Windows 7, well it ain't like no Windows 7 I have ever known. I didn't let it near my 2 music PC's, but I guess the time will come down the track away, where the choice will have to be made, I am happy to wait until that time when software or hardware requirements make the change necessary, but until then I am very happy with a rock solid, blazing fast Windows 7 (never really noticed any 'noticeable' speed up with Win 10 in any area)
 
One thing I will say though, is that the installation of Windows 10 went as smooth as, everything seemed to work fine, only the new Windows Edge browser seemed a little flaky, especially with these forums. The roll back to Windows 7 was also as smooth as, with zero issues since on all 3 systems. 
 
My beloved M-Audio Delta 1010 sound cards, of which I have 5 would most likely not work under Windows 10 anyway, there wasn't much luck under Win 8, and no hope for new drivers, and I don't really want to move on from them, certainly not to a USB/fire-wire alternative, and having 5 of them it will take some time for natural attrition to thin the herd, no doubt when that time comes I will kick myself for not moving on much sooner, but . . . they serve me well.
 
When the time comes to move on from Windows 7, I will be giving the Mac a serious look even if it means ditching Sonar, my other fav DAW, REAPER works fine on Mac, and I really do dislike Windows 10, even more than I do Apple. Hideous.
 
For my money, if you are happy with Windows 7, and it's working for you, stay put, by all means have a look at Windows 10 on another machine or whatever, then if you like it, that's up to you, but don't dive in head first with your main DAW machine, you may regret that :)

The theme of evaluating Macs to avoid Win10 is getting noticeable. Plenty of time to watch this play out, but if MS has a repeat of Win8, this may not be so good.

The better graphics resolution on fonts alone is worth the upgrade. It's like the fonts are a lot smaller yet much more legible than before - putting more info on the screen. Others might not have had the same improvements, but all of a sudden my 2 x 23" Samsungs actually LOOK better.
 
Apart from that, even my email PC which is an old DuoCore suddenly just kicks ass. Boots in about 20 secs max. My main PC also runs far better than before - and I seem to notice less bugs all-round.
 
I think Win 10 is a massive improvement - it's just a much more solid user experience.

There is one thing which will eventually force even the most reluctant of us to upgrade to Win 10, and that is that Noel hinted recently that Sonar support for Win 7 will cease at some point in the not too distant future.

Bristol_Jonesey
There is one thing which will eventually force even the most reluctant of us to upgrade to Win 10, and that is that Noel hinted recently that Sonar support for Win 7 will cease at some point in the not too distant future.

Mac, or for me, just dump Sonar, and just continue using Windows 7 and REAPER, it is still supporting XP, there are many choices, and Sonar is just a tool, other tools can do the same thing and buy more time. There are people still using X1, 8.5 etc, so if one so chose, they could possibly carry on for quite a few years yet if they are happy with the status quo, and weren't to concerned about having the latest and greatest. Then again Windows 10 may evolve into something acceptable to me, as it is now, I just can't bare to look at it unfortunately.

soundtweaker,
A comprehensive and useful list.  Can you please elaborate on the "Midi and audio bugs".  I am blissfully unaware of any with my present Sonar Pt + Win7 system but am happy to be enlightened.
 
Thanks.