Since this tread is kind of quiet for the moment I will risk one more comment on this off-topic discussion and try to swing it back to TFA a bit as well.
Of you go to TFA(PFA)'s website:
http://shop.perfumersapprentice.com/c-108-the-flavor-apprentice-world-of-flavors.aspx and enter "DX" in their search box; you will find a dozen flavors that are duplicate flavors that they have made specifically to avoid these questionable compounds. I have tried a few of them and they work nicely as a 1 for 1 substitute. TFA is not 100% on their labeling yet. I have found at least a couple of others that do not follow the "DX" labeling but appear to be non-acetoin/acetylpropionyl ( such as: Vanilla Bean Gelato appears to be a sub for Vanilla Bean Ice Cream , French Vanilla II and French Vanilla Cream are two different subs for their French Vanilla). If you are willing to do a little research; you can find alternatives.
One in particular I have been using quite a bit is TFA' s DX Bavarian Cream. You will find this is one of the more common flavors used in many of the recipes in this
thread to add that custard note you said you like.
`Nough said...
Other than Welcome!