Opinions on Trifexis

My vet recommended Trifexis for my 4-month-old puppy. I read some horror stories on the web, but they seemed to be mostly anecdotal. I gave Trifexis a try, but the next day when I feed my puppy his breakfast, he immediately threw up.
   
Now I've had enough puppies to know that occassional vomit is no big deal... there can be all sorts of reasons. But after reading the bad stuff about Trifexis, I'm kind of freaking out.
   
Does anyone have experience, good or bad, that you'd like to share?