Posted for Jack Cowell <jackcowell@optonline.net>:

 My WSI system can lag five minutes or so, but it seldom does. Further,
 the lag time is displayed on an MX20's screen so you know what it is and
 WSI says that lag is used to cross check inputs from airborne and ground
 sources so that what appears on your screen is vetted. If anyone wants
 more information on the WSI product and upcoming developments, I've
 found Paul Devlin at WSI to be helpful. His number is (978) 983 6766.
 One caveat: knowledgeable and helpful as he may be, his job is to sell
 WSI products. BTW, I love mine and if it were inop for any reason, all
 but the most benign IFR flight for me that day would be scrubbed.