Photo Stream access on pre-Lion Macs I have a machine not running Lion because of software Lion does not support. This machine is currently my primary household media hub, and it would be very helpful if it could take advantage of Photo Stream.

http://www.apple.com/icloud/features/photo-stream.html indicates that Photo Stream supports both Macs and PCs. If there is a PC client, could pre-Lion Macs take advantage of it under emulation to access Photo Stream data?
Yes - your example of running a supported OS in virtualization would let you use the officially developed and supported Apple client software to tap into the photo stream. Once you have the software running, it should be fairly painless to get the files to disk and then available for viewing on Snow Leopard.

It's technically possible to virtualize Lion as well while running Snow Leopard as the core OS, so you can choose if you want to use it or Windows OS to get your iCloud sync on.