You don' thave to use Cisco Gbic if you don't want to.

Elemental Network Consulting - Undocumented Cisco Commands

Here is a IOS command you might find helpful if your budgets are tight:
service unsupported-transceiver

You will get this warning how ever
Warning: When Cisco determines that a fault or defect can be traced to the use of third-party transceivers installed by a customer or reseller, then, at Cisco's discretion, Cisco may withhold support under warranty or a Cisco support program. In the course of providing support for a Cisco networking product Cisco may require that the end user install Cisco transceivers if Cisco determines that removing third-party parts will assist Cisco in diagnosing the cause of a support issue.


Not bad though, just keep a few Cisco gbics around for troubleshooting.



Full disclosure: Haven't tried this (yet). All our gbic's are 100% Cisco. And by that I mean, Cisco bought gbic's from the same company that you would (if you wanted to save $) and they put their Cisco logo sticker and idprom on them, then sold them to us for much more. But I'm sure the sticker makes them better some how.