1. It is a very heavy framework.
2. It will eat up lots of your valuable memory.
3. It is buggy, etc.

• Prefer using “session.get(classZ, ID) instead of “session.load(classZ, ID).Load always returns the proxy to avoid getting LazyInitializationException.
  
• Always set “lazy=true” for collection mappings and use “join fetch”  in HQL or “setFetchMode” in criteria to retrieve collections.
• Use surrogate/dummy id in data model instead of composite keys and override equals / HashCode method using the business key to identify uniqueness.
• As HibernateException is Runtime Exception never catch them at business layer and have them be propagated to UI Layer.There are several benefits doing this.
  
• Write Custom UserType  for type/code values with corresponding Java Enum class. Prefer using Criteria API to build the SQL query instead of HQL.
• Careful implementing toString() method for printing collections to avoid getting org.hibernate.LazyInitializationException
• Many-One mapping should preferably have lazy=“false” and One-Many “lazy=true”. Avoid N+1 Query problem using eager fetching or “batch” setting.
• Don’t retrieve to much data in one query and use paging, fetch strategy, and carefully using the join to get the data needed.
• Use 2nd (JVM level) caching for mostly read only data’s.
  
• Use query cache for read only data that is always queried the same way
• print only atributes which are mapped through ‘property’ element
• DO NOT print any collections  as all collections should be marked as ‘lazy=true’.
• object (many-to-one) should ONLY be printed if marked as ‘lazy=false” and fetch=’join’
• Avoid using <key-may-to-one> inside <composite-id> use <key-property> instead
• Avoid using hsql  as much as possible, prefer detached Criteria or Criteria Instead.   Very Very Important
• Do not ever perform bulk operations with Hibernate.

Any more points ?