Without CLMUL instructions, GCM is either very slow or potentially sensitive to cache-based side-channel attacks (regardless of AES being the underlying cipher).
The EAX mode of operation is more secure - though not very popular for some reasons and not part of any TLS cipher suite.
The patents may have killed it. Even "free for open source" can be troublesome if you're worried about putting free software into an appliance and getting trapped. Easier to avoid patented algos entirely.
But yes, definitely the fact that there were patent grants hurt it a lot in adoption before; even when (as in WiFi) it was one of the contenders, CCM is more common.
A few things do use it: off the top of my head, I think Mumble does, although I think that's an earlier variant (OCB2, perhaps, rather than OCB3 as documented in the RFC?).
I'm also looking forward to the results of the CAESAR authenticated-encryption competition - http://competitions.cr.yp.to/caesar.html - there's a lot of competition, and quite a few entries fell and have been withdrawn. The current version of OCB is among the current list of contenders, among several other interesting candidates.
For an example, this came up in the thread where OCB was proposed to be added to OpenSSL. You think you're free and clear, and then you're not. http://marc.info/?l=openssl-dev&m=136016226304441&w=2
Then came the OpenSSL specific license. That license probably applies to LibreSSL today, but now there's a Ship of Theseus problem. How much OpenSSL does one need to keep to qualify? And of course, the OpenBSD IPsec stack is completely unrelated to OpenSSL.
How so? As far as I can tell, the "open source" grant, covers everything under a BSD license (among other licenses) -- and holds no provision for "military use". I don't see how anyone using the [ed: algorithm, not code] under license 1, could become subject to license 3?
The OCB patent grant at the time specifically required GPL, which I believe played into the decision to release Mosh under the GPL. (It now has a very wide patent grant, permitting a few options including all non-military software use, both closed and open, but GCM was already winning by then.)