123 Mac Mini
I must admit that I was running the Lion GM for a couple of days before the official release. I didn't try any software updates. Whilst the Mac Mini seemed OK, there were a couple of issues with it not waking from sleep (I use it as a HTPC, so I need to be able to wake with the remote or on a schedule to record programmes). I reverted to Snow Leopard and was forced to do a format and reinstall when the downgrade didn't go so well (I thought I'd be able to just install 10.6 over 10.7. I thought wrong!)
Ok, I did test this with macmini and here are the results:
The short answer: you cannot run 10.7 Lion on your 'C2D upgraded' macmini.
The long answer is that yes, you can install it using the hacked Lion installer but there are things you cannot change:
due to EFI (BIOS replacement) being 32-bit only your kernel gets booted in 32 bit mode, too despite having 64-bit capable CPU.
That leads to all kinds of bad situations: you cannot install any updates nor programs designed with Lion in mind (they fail on the install). for example, you cannot install Java on it. The only thing did get installed was the new 10.4 iTunes since it was released for SL, too.
So, given what I've learned with this little experimentation I'll be reverting my macmini back to SL and start saving to buy this new'011 beast
Unless anyone reports any major progress with Lion on an older Mac, I think I'd be ending my experiment here. Snow Leopard is running mighty fine after a reinstall and I have no major need for the Lion multitouch features as I tend to use it in full screen with a remote control from the sofa anyway (Whilst I'm here, can I heartily recommend EyeTV and Plex if you watch TV on your Mac). Those 2011 Minis look pretty nice as well...
Thanks for all your comments and do let me know if you have any further success with Lion on an older Mac.