That depends on who you talk to. Some people find it acceptable, while others regard it as unmusical. I'm in the latter camp.
As for you, whether or not you allow yourself to dance starting halfway through the measure should depend on context. If you're out social dancing, you can decide for yourself what feels good and go with it. At a competition, however, I wouldn't recommend it. As I said, there are some people who find it acceptable but some who don't. So if you do it, realize that you're risking losing marks from those judges who do consider it to be off-time.
Regards,
Jonathan