Okay, Windows 7 Lesson. In addition to the comparisons made above me:
Vista was a flop. No ifs, ands or buts. Though it had quite a number of interesting concepts and features, poor execution, design and planning doomed it. And that was without the consistent law bending that Microsoft seems destined to try to get away with. Many Windows users never made the jump to Vista, with good reason.
But, Vista wasn't to upgrade XP in it's own right. XP has been a mainstay system for both personal and business clients for years, with at the time Vista was produced the XP-64bit OS was still able to handle any hardware on the market for it's market. After the ME debacle, the smart move would have been to hold onto a stable system and support it as long as possible. Now Microsoft does have the business share to get away with some bad choices, but the management isn't a bunch of morons.
No, Vista was prompted by the IP issue. Currently the net runs on IP4, being the protocol which the IP address uses(The address every device that ever connects to any network needs, its pretty much like your house address for getting your mail) was running thin on numbers. So IP6 was developed so we wouldn't run out of numbers (Exponential scale on this one, the increase is a bit sick) but this brought about a new problem. XP couldn't handle the IP6 protocol.
This prompted Vista. Vista was Microsofts original platform and answer to conversion to IP6. Now, as I've already stated, Vista failed to stick to the general public and the corporate scene. Microsoft tried to push the issue by cutting support for XP, but this only made problems worse.
Microsoft needed a new answer to the IP6 problem, because if they didn't have a good, solid system as good or better than XP on all fronts then they would lose out their marketshare to the Mac OS X (Since said OS runs on Intel Chips. The Mac/PC Wars are over, Mac Lost, PowerPC died, now we are forced to the throne of the Intel design. A Modern Mac is a PC that costs twice as much, is in a white funky case and has the Mac OS with it). If Microsoft lost the marketshare, then they wouldn't have the resources to stick to the business models and tactics that they have been relying on, and they wouldn't have the loyal fan base to keep them going either, it would be a drastic change for them.
So to keep the status quo, we have Windows 7. A supposedly solid OS that you can upgrade into without any problems, though upgrading hardware too, so your computer will be well prepared for the IP6 conversion (Which isn't slated until something like 2016, if I remember right, so no hurry or rush to be prepared)
Eventually you'll want Windows 7, it's much better than Vista, no doubt about that. And with XP having a set Death Clock as it were, Xp users are going to have to migrate to a new system. This is the reason why Mac is capitalizing on those mocking New Windows OS commercials, our choice of OS is rather limited.
And if for some reason I am wrong on all accounts and merely blowing smoke out of my arse, then someone please correct me so I can stop making an arse out of myself.