I'm a former I-300 / 6035 Sprint customer who made the jump. Absolutely no regrets - VZW service has been great (like having a dedicated data support number unlike SPCS forcing you through the call queues...). I had stopped by a local mall SPCS store before switching and found I was #22 in line to get help. The customers in the store made the Star Wars "bar scene" clients seem normal by comparison!

i-500 was rumored to be out today but is still MIA.

SPCS business connection personal edition (ie checking corporate email) was their best feature and a near show-stopper. I ended up with Laplink's PC Everywhere instead ($29/year for service if you have an older version of Laplink). Works great - unbelievably faster - but limited offline use. It works for my purposes.