It is much faster than a transplant, it works really well once we made the update software (before there were minor problems for estimating the required espacedique but it resolved.
I heard that there could be problems locators and time code if exported to the HD-24 after editing (on samplitude) but I've never experienced this kind of trouble because I do never re-exports to an HD-24.
I use the HD-24 for the live recordings where the PC is a risk of a crash too big and I export to my PC to the mix and I've never had a problem.
I do not have Fireport or HD-24 but I use regularly.
If I had to buy one I would choose 24 tracks without a doubt the HD-24 but I find the Fireport a bit expensive anyway and I think I will rather subculture ADAT to my PC at first anyway
HIGHLIGHT: fast and convenient