Had a host of problems, JB update fixed most of them but phone was now slooow to open and close programs and project butter was more choppy than butter.

Performing random acts of desperation, turned power saver button in notification on and off and phone was immediately (and remains, so far) as responsive as it's ever been.

Power saver seems as "useful" as fastboot; I hope HTC will let us disable it (and get it out of notification) in a future update.

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