Definitely agree about the feeling you get from a single, probably why I bought a 690 Duke. I would seriously like to try a Street Triple/MT-09 though.
I've probably got one of the more characterful IL4's - the one in the old CBR 250's has a gear driven camshaft and goes to 19000RPM
I've got one of those as well, it's hilarious when you look down at the speedo and think your doing silly speeds when your only doing 70! Its a fantastic sound.
It's a lovely thing, such a smooth engine due to the hilariously small pistons