In my Kombi, which is my daily driver, I generally fill up at United whenever possible, and use either full standard 91 octane, or occasionally if I'm feeling a bit frisky, I put in around 25-30% Boost 98... as in, for every $20 I put in, I put in $15 of 91 and $5 of 98... I suppose you could say I use the high octane stuff as a performance additive to the standard fuel. I really do notice the difference... gives you a massive kick in the seat when ya leave the station hehe. I dont fill up solely with ethanol blends, as it causes pinging in a few of me mates VW's, and it is also detrimental to the fuel lines... not a good thing in a dub.
As for the VN, I generally use the United ULP95 or equivilent cos it's generally the cheapest and the Commodore and its fuel plumbing dont complain about it.
The VH generally just has standard 91 ut thru it most of the time, altho not being registered and only being run every couple of months, it rarely has fuel put in it. LOL
Cheers!