My recommendation would be to run your own DNS on your own IP addresses. Even with the IP shortage, you should be able to get a small block delegated to you that you can use for your mission critical apps. Once you've got that arranged for, its a fairly trivial task to find a registrar with policies more complimentary to your business.
If its mission critical for your business, then you can't afford to think like a victim. Take charge of your infrastructure where you have to. Relying on third parties is lean, but not always effective - a small amount of fat in the right areas can give you a lot of flexibility (and insurance) that you might not get when you rely on a third party.
I work for a registrar, so here are my biased recommendations - me (hover.com) or EasyDNS. But don't take my word for it - do your own homework. Its worth knowing what your risks are and no amount of free advice on HN can replace that.
If its mission critical for your business, then you can't afford to think like a victim. Take charge of your infrastructure where you have to. Relying on third parties is lean, but not always effective - a small amount of fat in the right areas can give you a lot of flexibility (and insurance) that you might not get when you rely on a third party.