One of the oft repeated objections to using NHibernate is that there isn’t someone that you can officially complain to. Some organizations put great store in having someone to officially complain to :-).
The NHibernate community, especially the NHibernate Users mailing list is active and thriving, and a large percentage of the support questions that you may have can be answered there, for free.
However, there are situations where you really do want to have someone to call to get you out of the foxhole. And there are organizations that will not accept a technology unless they have a support contract.
I mentioned before that my company is providing commercial NHibernate support, but so far it has always been on a case by case basis, and mostly by request. I am happy to announce that we are now offering a Commercial Support option for NHibernate.
If that has been a challenge for adopting NHibernate, or if you find yourself struggling with NHibernate and require assistance beyond what the community will provide, you have additional options.