The Windows and Mac versions are not equivalent at this point, though as the moderators have said time and time again, this is the eventual goal. No “beta” software is “ready for prime time,” so any expectation in that direction is misguided, IMHO. Patience is called for, I would think.
My understanding is that the goal is to go to release with something like the 1.5x equivalent Mac functionality, though 2.0 features that have been proving easiest to implement have been getting into the Windows builds. Having said that, I’ve been using the Linux version for some time, and for serious work, and have encountered no show-stopping problems that were not also present in the Windows version. And very few of those, I might add. It just works, from my point of view.
If your XP build is SP3 or later you shouldn’t have any issues installing Scrivener in VirtualBox or otherwise. I got it running without adding anything. VirtualBox running Windows 7 works well with Scrivener out of the box as long as I turn off Aero. It runs okay with it on, it’s just a tad on the sluggish side for window creation/takedown, given the relative lack of code optimization at this point in Scrivener. I wouldn’t run Scrivener using VirtualBox unless you have a processor that can handle the load and has hardware support for virtualization, though most of them are–and do–these days.
I’ve given up completely with Wine, by the way, since I haven’t been able to get it running with b35.
The real problem with Linux support is that bug reports for that environment go largely ignored and that there is no official release package, just a tarball (“packaging” being a distro-dependant thing), which frequently leads to problems, so I’m not sure what the Linux version is for other than a good-will gesture, or something, which is a pity, because, really, it works fine, for me.
The lack of VirtualBox support probably means that there is no official test-bed for regression testing in that environment. Considering that VirtualBox is likely to be the environment of choice for Linux-based Scrivener users for the foreseeable future I think it would behoove the company to make a move to secure that market, especially considering that doing so would be relatively inexpensive.
But then, hey, your mileage will vary, and what do I know, after all?