[soult]

If either you, or your old provider do things right, there is no downtime at all. In your case it looks like Network Solutions kinda screwed you over.

Here's the correct recipe: a) Tell new registrar about incoming domain transfer, make him already set up nameservers. b) Set the new nameservers for your domain. c) Actually transfer the domain.

If either your old provider is nice enough to not shut down your name server as soon as he receives the transfer request (which won't benefit him in any way, because he is just helping an already leaving customer) or you follow the recipe from above, you will have zero downtime.

[jaylevitt]

This wasn't even a registrar transfer, just a DNS repoint from NetSol to Route 53. Amazon was all set up before the transfer; it was NetSol's screwup (which is probably some ancient set of CGI scripts) that caused the problem, and there was no way we could have avoided it even if we had known exactly what would occur - NetSol controlled both (a) the registry data telling the root servers where to find our SOA, and (b) the name server that the old SOA pointed to.

People using GoDaddy for both registration and DNS could find themselves in exactly the same predicament, so it makes sense that they'd want to do it carefully.