Some points:

1. Exceptions in Hibernate3 are now all RuntimeException.

2. Problems with committing and closing a Session can be easily solved by 
using an Interceptor approach (either roll your own SessionFilter, 
proprietary EJB Interceptor, or use the built-in support in JBoss AS).

3. Usually all problems with lazy loading and/or clear boundaries for 
units of work (thats what is called "live" scope on this page) are easy to 
solve once you think about interception.