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Yes they can both bitset and with the latest firmware they even retain the setting. As far as problems go, I wish I could say no, but they have many problems mostly relating to media burn quality at higher speeds. If your happy to burn at 8x until the media or firmware gets better, then fine. If you want 12x and 16x now, then look at other burner like NEC, Benq or Pioneer. See [thread=123733]this excellent review[/thread] of the 1653S, by OC-Freak.