Ooh! The faster speeds would be very welcome, I was bothered by the slowness of the AR488 but I assumed that was just how GPIB was (I had no baseline to compare to). I'll switch over when I get a chance.

That user's project also looks very interesting - My TDS684A's CRT seems to have died, and rather than fix it I could switch to using a software scope.

The upcoming V3 adapter reaches even more than 1 MByte/s with my fastest instruments. Unless you connect long GPIB cables to it, because capacitive load slows down GPIB as it self regulates speed down in the way GPIB is designed.

HPIB/GPIB itself should be reasonably fast, I think NI had some later revisions that were even faster. If I had to guess there will be two big hardware bottlenecks with the open source dongles: almost all of the 8-bit and cheaper ARM boards only do USB FS (12 Mbps, so 1MByte is pushing it) and most of those boards don't have any hardware acceleration for managing a parallel bus like GPIB. Even switching up to a Mega/Due form factor means you could potentially read the status and entire data byte in one read.

FWIW I'm working on a buzzword compliant stack for ARM MCUs interleaved with writing some HALs for Embassy. It'll be interesting to see how it compares. While I'm waiting on a replacement Chinese clone I decided to order a few more boards (Atmel, NXP, Renesas, STM), level shifters, transceivers, and whatnot from DigiKey to play around with.