IMO Home Premium is great. Ultimate for me just takes more space.
Also, the Core 2 Duo 8 series mobile is better than a 7 series in that Acer...
The only reason why I recommend Ultimate or Business is for the Microsoft Advantage program that allows you to downgrade to Windows XP Professional at no extra cost(I do like my options, and with the criticism regarding Vista I keep my options open).
I know the 8 series is better but is it R 2 000 better? One must also note if you compare the Acer against the HP and Macbook that the Acer only has a nVidia GeForce 8400M, so one must also take it into consideration.
For me it all boils down to value for money and in my opinion get yourself the Acer and then you have a extra R 1000 to buy yourself a carry bag or other IT goodies.
Regards,