Is It OK to Use AD Issued Computer Certificates for IIS?
There's no issue with running local certificates at all. Many enterprises use an internal CA such as AD-Certificate Services to manage and automate the creation of certificates for their servers. It's just as secure as a public CA as long as you distribute the certificates out to your clients and keep the private keys secured and private.
is there any reason to not use them for https bindings on servers running IIS?
Nope.
Where the cert comes from is irrelevant as long as it's trusted and has the appropriate x509 extensions for what you intend to use it for.