I'd also be wary about taking part in a beta where the work that I do while testing might become inaccessible afterward. When my husband got his laptop, it had Word 2007 preinstalled on it. Since it opened his previous documents that he'd made on my computer (which has a legit copy of Word 2000 on it), he went ahead and opened, edited and saved documents.
Fast forward a bit. He starts getting messages that he only has X number of uses left for Word 2007. When he calls the laptop people, they tell him it was a limited use installation, and he'd have to pay $XXX to get the unlimited use version. Thankfully, there were backups still on my machine, and the changes he'd made were relatively easy to re-construct.