If I'd read this thread, maybe I wouldn't have installed Lion. Ouch. I downloaded Lion (which took forever). I then made a backup of the install app, following the method suggested over at ars. When I was satisfied I had a backup of Lion (so it couldn't delete itself after install), I let the install run. It finished without incident. (Whew). One thing I did before starting was I spent some time in disk utility checking over the status of macintosh hd. For instance, I re-checked to make sure the partition table was GUID. I had recently upgraded my HDD and I ignored the whole GUID partition table instruction. Luckily disk utility set it up that way by default. If it wasn't GUID, I think the Lion install would have simply refused to start but I can't help but wondering if some partition table issue is related to some of the issues reported in this thread. I hope you guys get your problems figured out or at least get back to Snow Leopard.
I think it's more likely that my problem was not repairing permissions before installing, but I couldn't prove it since I tried so many things.