You're going to hear both sides of the story consistantly. Lots of people have has nightmares with the tiger barbs, and other people have had no problem.
I have 5 tigers in with a firemouth cichild, 2 rosy barbs, 1 redtail shark, and 1 cuckoo cat, and everyone gets along fine.
But I went through a few tiger barbs before the 5 I have now settled down. They did kill one of the original I had...
I started out with 4, one was being severly picked on, so i got two more out of recommedation...
When I brought home the new 2, they had Ich, i removed the one showing the white spot and put him in a quarantine tank...
the picked on tiger barb never was left alone, they continued to pick on him and eventually he died. eventually i put the other tiger barb back with the remaining 4, totalling 5. and now that group of 5 is all cool with each other, and cool with the other fish.
so basically, it took a while to sort it all out, but now they are happy. I'd say avoid them if you don't want to take a risk.
- kip