I have installed Windows 10 and I don't like it. My feedback follows (a section about drivers is further below).
General impressions
With time going by and with the various versions since Windows 95, users have been having less and less freedom when it comes to customizing the system. Windows 10 is no exception to that: "customizing the system" has never felt so much of an oxymoron.
The light gray color of the title bar of windows stays the same whether a window is active or not. And you can't change the color. And this is one thing among a myriad: the small task bar icons (40% smaller, ballpark figure) that can't be made bigger or that will **also** change the size of the text, the white line pictographs, the varying sizes of "live thumbnails" in Alt+Tab, etc. I don't find my way through this system and I just don't get what Microsoft is up to changing everything for the sake of changing: Windows 10 restores the oh-so-logical left-aligned window titles whereas in 8, they claimed centered titles made more sense, Aero came with Vista and saw its last days with 7. The classic window frame is now gone and replaced with a one-pixel wide line surrounded with exterior shadow, like on a web page. Yuck. It's all trivial but it's very telling as to Microsoft' replicating the "we know better" attitude of other consumer companies. I know some will say "does it matter?" but if it were so anecdotal, why was it there in the first place? and isn't it still useful to some? It's like screensavers, you know. Unless we are all to have the same taste and needs, like identical robots.
What I hate the most is the slowness, ie the fact that yesterday, with the same laptop, peripherals and components, it took me 45 seconds to reboot the laptop to the login screen. Now, it takes almost 4 minutes (3:40)! (Yes, it felt so long that I clocked it.) That includes a one minute period during which the screen is just black and nothing happens: no disk drive noise, no activity on the screen, no fan turning faster, nothing. Just nothing.
Everything is slower, even opening the WiFi networks panel is. I feel like I'm back to Vista. I now have 33 seconds to hibernation and 35 for resuming. That's 50% more than with 8.1 when I had even more programs opened.
.NET apps that I've launched (Altaro BackupFS, Countdown timer) feel more sluggish.
It's too phone/tablet oriented; just see the notification center or the settings window. We were used to icons, which helped find one's way quickly, now it's all monochromatic pictographs with greyscale text.
And the fan is constantly turning even when the CPU usage is under 4% (like when writing this post with no other program than Firefox running).
And I'll probably restore the Windows 8.1 system since I took the precaution of saving it using CloneZilla (but I'll probably be nagged by GWX.exe, the Get Windows X executable). To those who are having cold feet trying Windows 10, I've read today that downgrading is allowed by Microsoft but I don't know whether it's handled by a tool of theirs.
The good thing with upgrading was that everything (except Classic Shell, which was removed in the process) was kept as-is whereas after upgrading from 7 to 8.1, I had to reinstall all programs in Program Files. I have not seen any problem in any program except Process Explorer, which had some columns simply vanishing from the set of columns while being reported in the settings as visible. Also, the mousewheel is now working in lists (such as that of the default application per filetype) of system windows and dialogs. No search box paradigm (ie search boxes to filter lists and windows) implemented though.
About drivers
With the exception of the touchpad, the drivers were all the same before and after the upgrade.
The touchpad still can't be disabled :-) even with the latest Synatics driver from August 2015. Pointer inertia has also not returned.
When resuming from hibernation, only the laptop's screen was reactivated: the external monitor hasn't been, which forced me to go to the screen mode (replicate, extend, etc. – of course, much slower too) and switch to replicating the laptop's screen to external monitors before switching back to extend again. Of course, the layout of windows is screwed.
The webcam works, at least in Skype.
On resume from hibernation, the external speakers are **sometimes** (I don't know exactly how often) not reactivated and sound comes from the laptop speakers, which is precisely the problem that the very driver which I installed from Realtek two months ago solved after the upgrade from 7 to 8.1. Worked flawlessly on 7, didn't work at all on 8.1 then started working flawlessly again two months ago with the new driver, then no longer works. Go figure. [UPDATE: when resuming from suspend or hibernation, with a speaker jack plugged in through the process, sound comes from both the laptop speakers AND the external speakers.]
Last Dell machine, for sure. I can't understand the lack of support for such expensive machines. 8.1 was out in October 2013 and there was already no continued support for a laptop I had bought in November 2011. The attitude is unacceptable, all the more when on many systems including the L702X, most current drivers are drivers built for Windows 7 (and timestamped 2006!) and the driver model is said to have not changed in the last 4 iterations of Windows.
Hope this helps someone :-)