Is it okay to build Mac App Store apps for 64 bit arch only?

Question

I wonder if I should still support 32-bit architectures these days in my new apps. I only target Mac App Store.

Does Snow Leopard ever run 32-bit variants? (I guess yes, on older Core Duo CPUs that don't support 64 bit mode?)

Does Lion ever run 32-bit variants? (I guess no?)

The reason it's tempting to give up 32-bit arch is to use the new Objective-C runtime (which, for example, allows synthesized ivars).

UPDATE: published 64-bit only version. So far no reports about not being able to install it.

Answer 1

At this point I would say it's alright. Mac OS X Lion can only be installed on 64-bit compatable computers.

Anything above an Intel Core Solo or Duo ( Core Solo and Core Duo are 32-bit Intel processors), is 64-bit compatable.

Hope this helps!