Network Taps

In the class last night, we briefly discussed network taps. The name that came up was Net Optics. However, reading this page on Wikipedia, I see other manufacturers. A couple of people in the class mentioned Net Optics as being very good, although they mentioned they were pricey. Wikipedia's page lists some other vendors: Comcraft, Datacom Systems, Network Critical, and VSS Monitoring. None of those names were mentioned so I'm wondering if anyone has any experience with them. Any thoughts would be appreciated.

[edit: I just saw this in my drafts folder...I don't know why it was never published.]