I don't think Microsoft really give a toss about individual breaches of the EULA, their business focus for the OS market has always been volume customers & enterprise licences

I've gotten some very nice responses here, thank you all. +1 all around.
It indeed seems that Win7 RC is the way to go for me at the moment. I'll ask around at various shops to hear if any good upgrade deals to Win7 are coming into place (as they well should given the relative failure Vista has suffered).
The video card I'm getting is the beefy GTX 295, which boosts exactly 1792 MBs of on-card RAM. That leaves ilttle to run a next-gen OS on with a 32 bit system, so I'll need 64 bit and aiming for 4GB physical RAM on top.
One more question. Say I have more than one PC that needs a new OS install simultaneously. Would I, in theory at least, need to actually buy a new key? Or does the retail / OEM cover simultaneous installs on your own PCs?

No. For both OEM and retail it's one install at a time.

Unless MS decides to go with a Family Pack again, like they did with Vista.

Any normal copy is only for one system at a time. Microsoft is rumoured to be releasing a Family Pack of three Home Premium Upgrade licenses that is much cheaper than buying them separately. Leaked catalog listings indicate a starting price of $136.95, although there may be special deals for this and the price may change when it is officially announced.
Note that the Family Pack licenses are Upgrades, not full versions; you can do fresh installs with these but you will need to provide a valid XP/Vista license for each when activating. Additionally, the Family Pack seems to only be available as Home Premium.

On the topic of 32-bit xp memory. When eventually have to buy new computer I plan to make it Win7 64-bit /Win XP Pro 32-bit dual boot machine.
Would 4 gig or more memory installed cause problems or do I have to limit my self to say 3 GB of ram with half GB video card? Anything else I should take into consideration?

Why not get the Pro version of Win7, that way you can use the xp mode and shouldn't have to worry about dualbooting or memory sizes
I THINK that XP works perfectly with as much memory installed as you like but it can only use the first 4gb. The 9x operating systems shat themseles if you had more than a gig, you needed to edit some config files to get it to not crash all the time but I'm pretty sure that XP just ignores what it can't see

Fair enough then.

XP Mode isn't all its cracked up to be - a dual boot is a better solution depending on what you are using it for. Apart from anything else there is no 3D acceleration so it's basically no use for gaming. Microsoft's Virtual PC isn't the best bit of software either and can be quite slow compared to Virtualbox or VMWare.
I wouldn't say its that tricky setting up an XP/Win7 dual boot although it's not as easy as it could be. The only problem I had was getting XP to boot the first time - I had to repair my Win 7 installation to get that to boot again then manually add the XP option to my startup. There are plenty of tutorials around already.

Are you certain about this? I was unable to install Virtual PC 2007 under Vista Home Pro. When I tried it threw up a message saying it required Ultimate to install Virtual PC. I realize that my experience with this is with Vista/VPC2007, but I've not really seen any solid information stating that versions below Pro on Win 7 would allow this.

For best results, install the older OS first and then the newer OS. The newer OS will automatically detect the older OS and install the newer boot loader with both listed. Note that the boot loader is stored on the first active OS partition by default, so if you format that partition later on you will need to use the repair tools on the installation disc.
While this was true for Virtual PC 2007 on Vista (but not XP; it worked on Home Edition), the system requirements for Windows Virtual PC specify that it works on all versions of 7 (even Home Basic). This could change closer to release of course, but for now it's available for all versions.