For me Boo Boo, its really for geocaching. When I take the family geocaching, one of us has our eyes on the GPS to help us locate the caches.
The update lag on the TP is so bad, that we usually just manually enter the coordinates into our Nuvi and use it to close in on the cache. We use GCz on the TP2 for paperless caching, and to log the caches directly from my phone.