I remember when I first starting watching barney, which was during the sixth season. I was about four years old at the time so I actually enjoyed that crap.
Barney isn't an all around bad show, unless you've watched any episode after the third season. They never taught much educational things, but it was still entertaining to watch.
I've been watching Barney with my niece for months now and she really enjoys it. I kind of tuned out the show completely after they replaced the original kids from the first three seasons. It was just unbearable to watch after that in my opinion with all those new kids.
So all in all, don't watch this show. If you do decide to watch it anyways, stick to the first three seasons, the third being the best one. There's very little educational value in the show, and mainly is about kids with bogus smiles who sing about candy and friends and nature and all that shit.