Cisco doesn't use it (IOS is home grown, IOS XR is QNX, NX-OS is Linux), Juniper uses FreeBSD, Arista uses Linux, HP uses (I think) Comware (linux), Intel & Broadcom are pushing Cumulus (linux) on their reference networking platforms, Dell/Force10 is NetBSD based (and older Dell is VXWorks, I think), Pretty sure Brocade is Linux, but they've also used VXWorks. Don't know what Hauwei uses (that wasn't stolen from Cisco, or course).
Not that this is authoritative, but I've talked to a couple of execs at companies who were using OSS platforms for their networking devices (Nokia, Juniper, Force10, Arista) and all of them basically said OpenBSD wasn't a consideration because of the open hostility the people leading the project had towards commercial enterprises. No one was interested in betting the company with the threat of a "DARPA funding" moment hanging over them, much less someone who was more interested in dictating terms and making "statements" than cooperation on business relationships.
[edit for punctuation]
Nevertheless, there are some small companies selling things based on OpenBSD - even though, I'll admit, they are mostly companies started by OpenBSD developpers:
http://www.openbsd.org/products.html
You can also get some consulting & support:
http://www.openbsd.org/support.html
And, of course, there is always the strong possibility that some people are using OpenBSD while keeping it hush-hush and "under the radar" -- maybe even under the radar of their own management.
Make of this what you will.