MySQL 5 : safe update ?

[Frédéric VANNIÈRE <frederic@vanniere.fr>]

Hello,

Is there compatibilities problems between MySQL 4.1 and MySQL 5.0 ?

I need to move 4000 databases from one server to another (dump then  
import) and
I'm wondering if I can use MySQL 5 on the new server without breaking  
my customer's
websites.

Regards,

Frédéric.