Spice users: Any negative externalities after usage?

I smoked Spice for the first time a few hours ago, and, admittedly, I know it was stupid. I knew nothing about the drug and was told it was legal, so, naturally, I thought that it was harmless. Prior to my initial dosage, I had never tried any drugaside from alcohol, so, please, if you're going to criticize me for being stupid, don't bother-- I've been repeating that same line to myself even before I arrived home. Anyway, I had a panic attack whilst 'high' and felt as though I was blacking out every so often. I was forgetting where and who I was, and felt as though I was in a dream. Has anyone else experienced this? Also, has Spice been reputed or known to elicit any long-term negative health effects? I took three hits, and never will again.