How bad is it? It's better produced, but worse, than the original, which wasn't good.
Should you see it? No. Fans of the original will be disappointed; for everyone else, it's more of the same.
I hated "Blair Witch." Detested it. Abhorred it. Loathed it. So it took a lot to convince me to see a sequel. The sequel follows people who try to prove that the original wasn't a fake, with the expected outcome. It obviously has a bigger budget, but that makes the shaky "found footage" less believable. The acting is largely mediocre, with the exception of the guy playing the sheriff, who's terrible.