might just be best to wait until a little later then, it did take me around an hour and a half just to download, i imagine a bunch of people are trying to download it at the same time. happens with all big releases, not to mention Free releases!
I'm using the same software 10.7.5 and got the same message, but when I checked the specs it only shows the late 2008 Aluminum Macbook Early 2009. I have the early 2008 White Macbook so it's not compatible. Bummer