Being a Stuff It fan I was not happy that it did not work with Lion. I assume at some point they will upgrade or maybe they have by now.
I asked my Apple trainer which program he would use and he suggested I just compress the files on my Mac and not use another program at all.
It is really simple...
Using my magic track pad I two finger click on what I want to compress. (I think that is right click with a mouse but I don't use a mouse so I don't know.)
A menu opens and I scroll down to Compress. I let go and it is compressed.
So simple. And another program I didn't have to find and buy.