I got the update to Win 10 on a 3-4 year old Dell Inspiron laptop (4 GB RAM, dual-core CPU, running 64-bit Windows 8.1) last night. It's not our main computer, so I thought "Why not?"
Installation took about an hour or so, and was painless, and everything seems to run fine. All my installed programs and data were retained, and desktop icons were left right where they were on the Windows 8.1 desktop.
First impressions - it's a VAST improvement on Windows 8.1 - the Start button is back for one thing! The user experience is far more consistent as you swap between apps - it's very reminiscent of how Windows 7 worked, but with the Windows 8 "flat" look. My computer boots faster than it did under 8.1, and I felt "at home" straight away. It runs at least as quickly as it did before under Win 8.1, and my effective productivity is already better because it works the way I expect it to. (I never did get used to Windows 8's "split personality" of jumping between the modern UI and the desktop all the time.)
My advice: if you're on Windows 8.x, and you hate it, then upgrade to Windows 10 ASAP. If you're on Windows 7 and you're happy with it, then there may be no compelling reason to rush it, so you might want to wait a few weeks to see if there are any horror stories before upgrading - but I think when you
DO upgrade, you will be very happy with the new Windows 10 UI.
(Back up your data first, of course - I didn't lose anything in the upgrade, but you can never be too careful.)
I've got the Win 10 upgrade "queued" on a couple of other Win 7 and Win 8 machines and a Win 8.1 tablet - I'll install the updates progressively, and report back here if the experience is any different on any of the other machines.
The Windows 7 laptop is the oldest of the lot (about 5 years old, 2 core CPU with 2 GB RAM), but the update advisor says it is up to the job, so it will be interesting to see how it manages it.
The Win 8.1 tablet is a budget 8" Toshiba Encore (quad-core, 2 GB RAM, 32 GB stoarge) which was designed for Windows 8
http://www.mytoshiba.com.au/products...specifications . I may have to clear a bit of storage space to squeeze in the update, but I will be interested to see how the Win 10 interface works on a true tablet device.