One computer is anecdotal. I've got a house and a company full of Windows 7 laptops and workstations. (Three of which are on my desk.) Almost all crash related issues with this larger sample population have been with hardware and the very rare malware.
Windows 8 in the working population isn't a solution for the majority of productive users outside of the vertical markets that have a need for a tablet.
I never shut down my PC (Basically always use sleep/hibernate) and have it running for weeks at a time with the only issue being Firefox freezing up now and again.
Maybe the problem lies with the laptop? I never have issues with 7, but my experience is just as anecdotal as yours. Have you tried XP on it to be sure?
Going to go on a hunch and suggest its a dodgy driver then, or some piece of hardware windows is picking up that Ubuntu isn't. Its annoying that bad drivers still crash windows but the same thing happens on Linux systems.
Going to go with drivers again. The sad truth is closed source drivers can be as hit or miss as open source. By any measure I have tried, Windows 7 is considerably faster then XP for the gear I run, but only when proper drivers are installed (not the included Windows 7 ones).
It is annoying when you get something that's slower or doesn't work though. I was burnt by Creative with my Live! Drive and as such will never buy their hardware or software again, but I don't blame Microsoft.
My laptops 7 is a constant crash, constantly overloaded, reinstalled several times but I have to work on it.
Did not even think about installing 8...