never had any problem with them myself...but from what I gather, if your nips start to get itchy or irritated, then you need to either start nolva/ari/liquidex etc..., or up the doses if you are already using an anti-e
Other people can give you some opinions on what anti-e they prefer. I personally have only ever used arimidex...took it throughout my cycle at .25 eod, and had no probs.
J