I got this voucher with my new Macbook Air but don't really know what to spend it on - any suggestions?
So far I have bought the MAS version of 1password with mine.
Saving some of the rest to buy a copy of Lion for my older machine.
Also picked up Daisy disk to keep an eye on my SSD space.
I dont think you need to buy Lion again to install on your older machine, im sure you can download once and if you sign in with the same account on the other machine you can download and install again and Apple are fine with this
Toonbay is correct.
I bought lion once and was able to install it on two different machines using the same account.
Correct - you're not doing anything sneaky either, you're allowed to install software from the App store on any Macs you own or control.
I tried to download iLife apps to my desktop mac, but it told me that I had to buy it, even tho I have iLife'11 on my MBA. They are both on the same apple ID.
Maybe things you buy can be added to several computers, but the things you get when buying a new computer certainly can't be be installed on your old one.
Convert it to an itunes card.