The attempt at vanilla cream soda didn't work out all that well. There was some vanilla flavor and there was carbonation. There was also an overwhelming yeast odor. It swamped and ruined the vanilla flavor. I sampled it. Twice. jmaynard sampled it. I dumped it down the drain.
I have started another bottle, going lighter on the sugar and the yeast, and leaving a smaller air gap in the bottle. If I can get the yeast smell down to a tolerable level and still have carbonation, then I'll consider things a real success. As it is, well, who wants yeast soda? I certainly don't.