NexRad is only as good as the system it is sent through. Some spots are slow with reception. So getting timely information that's within minutes of accuracy is rare. I always plan for it to be 5 minutes ahead of where it usually is, and it works fairly well.

As stated above, it will also indicate a slightly worse condition than is actually out there.....definately in the name of liability. On-board is really the true source of tactical information if you are planning on flying close in to any precip anyways. NexRad to me is strictly for long-term planning.