Worst side effect? A gargantuan and horrendous addiction, one I had to switch to diazepam to get a grip on, and a year later still slowly and gruelingly tapering, with nasty effects, even at a 10% reduction of diazepam a month.
A benzo (or thieno if the pedantic folk want to get all, well, pedantic) addiction is the worst for those prone to them. I'd rather kick heroin ten times over than deal with this BS everyday.
I maintained on 60 mg a day of etizolam for most of 2012, with 100 mg days for recreation. Yes, tolerance builds fast, and yes, I have prior history with benzos. I never got any side effects different than those from classical benzos....less actually.
Use caution, and more importantly, self control...