Claims vs Forms Authentication

I am porting my website from ASP.Net to Sitefinity. It currently uses Forms Authentication and I have 3,527 logins, 832 that I would consider current. From what I have read claims is the better way of going, but I have a challenge, how do I get there from here. All of users are stored in SQL with a Hashed password, so I don't have access to recreate them.

So given that I have a few questions:

1) Is there a way of converting forms based to claims based with the forms password being hashed?

2) It is possible to run for a few months in both worlds, using Forms as the main one and creating the claims based counter part as they login?

3) Is all this trouble worth it? Is claims drastically better, or marginally better? I know in theory claims is more secure and quicker, but in the real world are we talking enough better to be worth the trouble?

Thanks

Randy Miller