Fortunately, hardware compatibility would seem to be much less of a potential issue. I've had no problem on either of the machines I've installed it on - even the integrated DVB-T TV tuner was picked up without any fuss - and plenty of fellow IT journalists I know have installed the system with very little trouble on all sorts of different PCs and laptops, both brand new and old with few major problems. The installation process itself, incidentally, is more streamlined than XP's too. If you go for a clean install you should have your new Vista system ready to go in well under an hour and you don't have to watch over it, clicking Next and filling in dialog box after dialog box as you do with XP.
Inevitably, for users with obscure items of hardware from small manufacturers, compatibility (i.e. your hardware partially working, or not working at all with Vista) may well be an issue. It's impossible for to predict how this is going to pan out with your system, so the best advice for now is to visit the Microsoft Vista website, download the Windows Upgrade Advisor and run it to see if it flags up any hardware that is likely to be a problem.
Of course this is assuming you plan on installing and running the 32-bit version of Vista. For those with 64-bit processors planning to upgrade to Vista 64-bit, the situation is more problematic. First, Vista 64-bit won't run any 16-bit code, full-stop. Now you may think you don't run any 16-bit software, but you'd be surprised how many cheap and nasty install routines actually still use 16-bit code. And anyone who thinks they might need to run legacy 16-bit software should clearly stick with 32-bit Vista.
Second, with Vista 64-bit you will not be able to install drivers that are not properly signed. I've lost count of the number of times I've installed drivers that haven't been signed since XP started to use the driver signing system. Many companies don't bother because the process of getting drivers signed costs them time and money. Unfortunately this requirement means 64-bit drivers, which are already thin on the ground, are even less likely to be developed. Clearly 64-bit software should run better on 64-bit Windows, but there's not an awful lot of this about. Not enough to make 64-bit Windows a viable choice for the masses just yet, anyway.
Software compatibility is generally excellent, but again there are, inevitably, some caveats. I haven't had any major problems with the software I use day to day, but there are plenty of applications that simply won't install in Vista, even in compatibility mode, or don't like the Aero graphics system (iTunes for instance). There's also an issue with security software, much of which won't work at all with Vista's new way of doing things.
The best approach here is to check the manufacturers' websites for updates – many have already posted patches on their websites and those that haven't are likely to do so soon.
Probably one of the biggest factors that will drive sales of Vista over the coming months is not the way it looks, its extra security features or even its new applications and tools. It is games.
With Vista the next generation of DirectX arrives – version 10 - and this time it will not be backwards compatible with earlier versions. What does this mean? It means, alas, that if you want to run DirectX 10 games, you'll have to be running Vista. No ifs, no buts.
Earlier games written for DirectX 9.0c and before will work - Vista uses a legacy version of DirectX 9.0c, which will run side-by-side with the new version – but you won't be able to run DirectX 10 on any XP-based system.
Now currently it's not an issue. There aren't too many titles in the pipeline for DirectX 10, but rest assured that will change soon, and when it does, you do not want to be left behind.