I tend to disagree slightly.
The learning curve from XP to Vista/7 is minor for most users. 8/8.1 on the gripping hand, are completely different in behaviour until you add 3rd party tools like
ClassocShell to get back normal start menu functionality. Do not be fooled the "Start button" in 8.1 does not give back the button and functions you are used to having.
I also disagree with many on how bad Vista was. It was a big change in the core coding of the O/S that meant that:
1. it needed new drivers for all the 3rd party hardware, (priinters, scanners etc) AND
2. it was where MS switched from what was originally designed as a consumer stand alone PC model, to an always online connected model.
What this meant was that for point 1, all the 3rd party hardware manufacturers had to produce new drivers for their equipment, but despite having access to the data they needed, at release they had only made them for their newest products. Leaving many with older gear out in the cold & having to buy new equipment if they wanted to use the new O/S. The drivers for the older gear eventually trickled out, but it took some years before most stuff was supported. This led to Vista having a poor reputation for supporting older hardware despite it being the 3rd party OEMs who were at fault.
Point 2 was in response to all the criticism that MS received over the 'permit by default' security model that had come from the operating systems DOS heritage. Other O/Ss (Linux and MacOS), were derived from UNIX which was always a network operating system, so it, and they, were always 'deny by default' except for specific user folders that you are granted access to. Switching to this type of security model meant many legacy programs would have issues, so MS made security workarounds for them, thus the grey desktop with the access request prompt that so annoyed many people. They were used to everything just doing what it needed to without intervention, but that is what gave the malware creators such free reign. This was lose-lose for MS. Either they could take the hit with upset users who were interrupted by security prompts, or they could take the hit for continuing to fail to address the industry security issues. No choice there, but still no win for them.
Windows 7 tweaked the security prompts a little so they are less obtrusive & made it prettier, but is essentially Vista service pack 2 with a different name to get away from the bad publicity surrounding the Vista name. In fact, if you notice all the XP updates are numbered KB5.nnnnnn (KB is for Knowledge Base) and the ones for Vista are KB6.0nnnnn. But Windows 7 is KB6.1nnnnn so Windows 7 is actually 6.1, (Windows 8 I have not got installed here, but I believe they may actually be KB7.nnn)
8 was designed by people who wanted a single user interface across all platforms, desktop, laptop, tablet and phone. But an interface for tablets & phones with touchscreens does not work for desktops with keyboard & mouse. So they gave it the ability to switch to the standard Windows desktop, but without all the features you are used to & many things are hidden in different places and can be very difficult to locate until you have learnt the 'secrets' to get to them. The Metro screen is ok if you have a touchscreen, but quite difficult for KB/mouse until you have sufficient practice.
There are rumours that Windows 9 (due in 2015?) will be a further step back towards 7 in user interface. MS are even now, apparently, looking at giving 8.1 away to vendors free to try & increase the uptake since it is so disliked as a desktop user interface by so many. Even if it is just due to the change. It is not a 'bad' O/S, as such, just a very big change in the way things are done and not entirely suitable for many of the PCs it has been installed on.
TL/DR
For now, I'd probably just go with a relatively cheap laptop or desktop with a Win 7 install. Unless you want to play games with high end graphics requirements or need it for significant data processing, CAD or the like. Any low to mid range PC will be plenty for email, browsing & watching movies.