I started a month ago and love it. I have yet to see anyone puke or bleed. I imagine if you push yourself to be competitive timewise that you may very well puke or bleed.
The cross section of people at my box ranges from middle age women like me, out of shape to very fit men and women. When I do a WOD, I am not coming anywhere near the times that the fit people get, but no one cares or says anything and everyone is very nice. They do a good job helping with the movements and offer opportunities to scale back on the weights with no judgement. 90% of the time I am unaware of what other people are doing.
As I do the WOD's I can see where an overzealous beginner could get hurt but at least at my box, no one wants you flailing around more weight than you can handle. Oh yes, they will let you take for ever to do a ton of push ups without telling you "it's OK, you can stop", but they are also quick to hand you a lighter weight if needed or direct you to ring rows if you can't do a pull up.
We also do a lot of weightlifting that isn't WOD's and that instruction is good too. We do do some max effort lifts, but again, form is the focus and no one cares if the beginner can only shoulder press the bar or can't do an overhead squat and again, the fit people are either helpful or simply too absorbed in what they are doing to care that you don't lift as much as they do.