I'm on a 27" imac with Wacom Intuos 4. Same problem with lag of certain tools (most noticeably with the healing brush). It was driving me crazy. I tried everything mentioned in this thread with no luck. I finally discovered the solution (for me). I hope this helps those like me who were looking for a complex solution before considering the simplest...I went into the Wacom preferences and changed the Tip Double Click Distance from 'Large' to 'Off.' Problem SOLVED. Now, no lag. Cheers!
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