What ORM to Run: telerik Open Access VS Subsonic VS linq to sql VS Active Record

Question

We are looking into using an ORM and I wanted some opinions/comparisons

The basic criteria we have for an ORM is: Easy to use/configure(short learning curve), flexible, the ability to abstract it away, easy to maintain

Here is a list of what ORM we are looking at and what our initial impressions are

1. Open Access - seems really easy for simple stuff, but doesn't seem to have a lot of flexibility, cost isn't an issue we already own it
2. Ling to SQL - looks very simple to use and configure but is missing some functionality
3. Active Record - NHibernate made simple
4. SubSonic - looks very feature rich, but haven't really played with it much

here are the ORMs we have looked at and ruled out

1. Entity is still in beta
2. NHibernate has far to much of a learning curve (we don't have 3 weeks to delicate to learning it)