Only if the download did not complete (can anyone confirm this?). For those who want to download the whole thing again (e.g. for another mac) have to wait until the Purchased Tab is back up and running.
I installed on my mac pro (purchased there) then went to my mac mini, opened the app store, clicked the lion link on the front page and clicked install.
I installed on my mac pro (purchased there) then went to my mac mini, opened the app store, clicked the lion link on the front page and clicked install.