I popped over to AJA Support just in time to see them withdraw support for the IoHD post Mt Lion.
I decided to back off and lie low in Mt Lion for a while, especially since Mavericks left out some basic support needed for my eSATA ExpressCard.
Back now with loads of great news.
1. An SSD has added 6 months to my 2010 MBP17. Yosemite's ticking along at new computer speed.
2. Motion is dead but FCP7, Soundtrack Pro and DVD Studio are fine.
3. IoHD is fine, but please note that I capture with VTR Exchange and edit in FCP later
4. Yosemite restored support for my eSATA card.
And lastly, a bit of googling turned up the directory /Library/LaunchAgents. In there I spotted and removed com.aja.iohdupdater.plist since no updates will be forthcoming.