Disclaimer: This post is based on my current knowledge of what the next version of Entity Framework will be like. That might be inaccurate or it might change until the next version is actually relased.
General Approach:
The main approach of Entity Framework (EF) is using their graphical designer tool to create an Entity Data Model and to generate domain classes as well as mapping from that model. There is support for other approaches as well, but that way of working will probably always be the main one.
NHibernate (NH) is a text based tool which requires the user to write all the domain classes and mapping manually, if you don't turn to third party software for code generation, such as MyGeneration of CodeSmith, or additional convention over configuration support, such as Fluent NHibernate.
Code Generation:
Code generation is a major part of standard EF usage, either by using their graphical designer tool or by using their command line tools. The availability of both GUI and command line tools is a plus since makes EF easy to get started with as well as allowing for more advanced usage that can be automated, for example in a build process.
Code generation is not supported by NHibernate, except for the schema generation stuff if you want to count that as code gen. You can get code generation if you turn to third party software though.
Database Schema Generation:
EF will add support for model first development, by allowing the user to generate a schema from an Entity Data Model. NHibernate has had schema generation support for a long time. The difference here is how you create your "model", as mentioned earlier.
LINQ:
EF will have improved their whacky LINQ implementation from v1 and NH have now reached version 1.0 of LINQ to NH, so there should not be any major differences between the two in that regard.
POCO:
EF will add better support for the Domain Driven Design approach and the use of domain classes that are separated from the data access layer. However, since POCO is not the main use case of EF I can't really see how their POCO support could ever reach the level of NHibernate. The POCO support in EF is still young, and to me it feels more like that it is a bonus if you are a POCO/DDD supporter and you find yourself working on EF for some reason.
The entire NHibernate framework is build for POCO development, by DDD people, and they have reached version 2.1 as well as taking advantage of all the work put into Hibernate on the Java side. NHibernate will probably remain the no 1 choice for the DDD/POCO/ALT.NET crowd for quite some time.
Lazy Loading:
The next version of EF will include support for automatic lazy loading. Automatic lazy loading has been an important part of NHibernate for a long time.
Learning Curve:
Both frameworks are complex and powerful, and hence take a long time to master. But EF is quite beginner friendly since it is integrated into Visual Studio, with its graphical designer tool, and since it can generate a lot of stuff for you without you having to know just about anything about the framework. However, if you want to dig deeper into EF and really learn the framework, you should be prepared to spend quite a lot of time using it.
NHibernate has a notorious learning curve, but some recent improvements have reduced it a bit. Now that LINQ to NH is at v1.0 the query syntax will be easier to understand for developers new to NH, and the Fluent NHibernate project is improving the mapping experience, and even working on automatic mapping, which is getting better and better all the time.