Hi,
Are you running with a debugger attached? If so, try running the app without a debugger. It's a known issue:
Navigation can appear slow when a debugger is attached and the map has the accelerated display mode enabled. The display can appear to "stutter" when zooming in, especially on tile layers. This is due to performance impact of the debugger interacting with .Net exception handling. The exceptions are within the.Net framework and are caused by cancelling in-progress web requests for tiles that are not needed for display. It is recommended to verify application performance in release mode without a debugger attached.
Cheers
Mike