There's been some discussion about how many interlinguists use collateral
orthographies. To produce some numbers, I searched the last 4 years of
INTERLNG (the largest Interlingua mailing list) for 3 word pairs:
Adding up all the occurrences gives us 88 percent for the conservatives and
12 percent for the moderate reformists. I'd characterise this as indicating
that the moderate reformed orthography is decidedly a minority choice, but
well within the spectrum of normal IA usage.
I should add that the more radical collateral orthography (which also drops
doubled consonants) is rare.