I was an idiot when making a spumoni stout (yes, I made tea out of pistachios for the batch), and to save about 50 cents, bought imitation vanilla instead of the real extract. It ruined the batch.... or so I thought. I had the first one on easter with the family, and it just killed me because the astringent aftertaste reminded me of cleaning solution (if scrubbing bubbles could describe a taste?). I had one last week and it had mellowed out some. I'm thinking that while this beer could probably never be great, the longer I let it condition in the bottle, the more drinkable it will become. I will probably let it sit for at least another month or two before opening another bottle, and I urge you to do the same. Aging has worked miracles for bad batches for me, I suggest you just give it some time. Then again, that is to be said for vanilla; I've never tried imitation fruit flavorings. Let us know what the verdict is down the road though for future brewers' benefit.