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I wouldn't touch an iOS beta on a device I actually cared about. It's easier to get out of the Mafia than it is to get a phone unregistered from their Beta program.
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Betas are done through profiles now you have to download either from the dev portal or through the public beta site. They used to be registered to developer accounts with the UDID. Now people can put a beta on their phone, roll back, and with an encrypted iTunes backup be on the public release cycle very easy.
My Apple products run betas the vast majority of the time and have done so for years without significant issues and roll backs are very easy with the right backups. A lot of devs do not have the funds to have an entire set of hardware just for app development and have to use their personal hardware. The public betas also allow Apple to collect a significant amount of data before builds go live to the masses. Craig Federigi did an interview with
John Gruber and said stability is way up (in the period they started public betas).