Using notes is never a problem. It is ‘how’ you use notes that is crucial. For example, you are only doing a five minute speech, then it may be a simple three by five inch card with one or two hand written words. Of course, if you are doing a half-day technical workshop, notes that are typed and on several sheets may be needed.
One key consideration to remember is the use of notes should never interfere with the connection between you and your audience. If your notes are small, compact and hard to read, you may lose your eye contact with your audience once too often. In this case, notes that are typed with a large font, on several numbered pages and can be read three to four feet away may be the best. This will allow you to glance quickly at these notes and still maintain eye contact with your audience.
Remember to think of notes as another tool to connect with your audience and not as a distraction.