Nice article from Danny Sullivan on this, check it out here.
In essence the thing to remember is don’t treat Google differently; that is what gets you in trouble. You can still end up getting slapped by Google doing things the “right” way, so be careful. However, if you have done everything you can to improve the experience of the visitor and not been silly (or dumb), then the penalty won’t last (you can appeal).
IP delivery or cloaking is a reasonable complex subject, so don’t go jumping in without some good advice. But most importantly it is not “evil” and Google has been reasonably consistent in modifying their definition to underline this.