I think you want to go ahead and "reserve" your download, maybe even go ahead with the download when it comes out on 7/29. However, I think you have a year to decide to take advantage of the upgrade. I still have two desktops, one on 7 and one on 8.1. I'll probably upgrade one of them right away and hold off on the other until things stabalize.
FWIW, the expectation is for several revisions to come out in the months following.
People who are in the "insiders" program are reporting various issues like you would expect with drivers, etc. The new browser is supposed to be super fast. I'm personally looking forward to Cortana on the desktop.