Vista is a nice OS, I will probably upgrade within time. However, before you go all buy-happy, here are a few warnings:
1) You'll want the Premium version. Home Basic is needlessly crippled, and Ultimate is needlessly expensive. Unless you're doing wierd developery things (which you'd know if you were) then you likely don't need ultimate. The "Ultimate Extras" are not liable to be worth the extra outlay - and if they are - you can always upgrade later with an in-place upgrade at a reduced price. EDIT: If you are planning on purchasing several copies under the Family Licensing plan, Ultimate might be more attractive.
2) OEM Versions - If you see Vista Premium for a price around $119, or Ultimate for $199, be very careful. This is going to be an OEM version. NewEgg, for example, is ONLY offerring the OEM version. If you buy OEM, be prepared to have to cough up for another purchase if you ever change hardware, as it will be tied to the machine you first install it on. You MIGHT get one major hardware change - that is debated and remains to be seen - but you certainly won't get more than that.
EDIT: Some sources are saying that the only restriction on OEM versions are that you don't receive manuals or support. This contradicts many other supposedly trustworthy sources, and I don't see anything "official" either way from Microsoft. If you want to buy OEM, I'd suggest waiting a while and seeing what actual user experiences are with OEM activation issues.
3) Upgrade Versions - If you see Vista Premium for a price around $159.99 - be very careful. You're looking at an UPGRADE version. This means that you're asserting when you buy the OS that you already own a legit copy of Windows XP. Worse, you can no longer just show it the XP media like you could in older versions. You actually have to UPGRADE an existing copy of XP. There's NO clean install option. This means 3 things. A. if you don't actually own XP, and are a reforming pirate, you'll get screwed as it won't install. B. If your system craters and needs reinstalled, you'll be spending about twice as long reinstalling everything, since you'd actually have to install your OLD XP first, then upgrade to Vista. C. Without a clean install, there may/probably will be "issues" with reliability, as historically, upgrades are never as reliable as clean installs. Some retailers, such as Best Buy, are advertising Windows Vista Premium at this price without any mention of it being an upgrade version. Forewarned is forearmed.
Generally, nobody will be offering Vista for a discount for a long time. Most of the "deals" will involved bundled applications, printers, other misc hardware at a "reduced" price, and often with rebates. The actual copy of Vista will almost never be reduced below suggested retail, and won't be for a while. So if you are determined to buy Vista, you'll be paying through the nose, and best to do it for the full retail, NON-oem, NON-upgrade version of Premium.
Good luck!
EDIT 2: I've had several people tell me I'm wrong on various bits here. I didn't pull this stuff out of thin air - I did research. The problem here is that MS has NOT been up front about any of this stuff. There is a lot of shady marketing going on, and ultimately only the user stands to lose by it. Much of this will become clear within the coming weeks and months as people actually begin to test the limits of what Vista licensing does and doesn't allow on various versions, and what workarounds may exist. In each case though, I have attempted to go with the most documentable sources.
