said by lutful:I have also found this to be true. Compatibility with programming software is also an issue. We use only National Instruments GPIB interfaces since we primarily program instruments with LabVIEW. While we have had various amounts of success using other brands there is always extra hoops to jump through and "issues" to deal with, while NI hardware is expensive it just works.
I just wanted to comment that some USB-GPIB interfaces have occasional compatibility problems. Unfortunately their drivers are also proprietary and vendors rarely update them. If you find a really cheap one from eBay and such, please check online for the manual and latest driver.