I was told that I must do this and I'm so glad I did. If you are worried that this is too hard, don't worry. There are a lot of steps, but they are not steep steps, so most of the time, it just feels like you are walking. There are four flights of narrow steps (walking up and then down a steep ladder). But you practice prior to the start of the climb so you are comfortable. That will be the most challenging part, but so very worth it! The guides are awesome and it's very safe.
This tour does't have to be the length of time that it is. During vacation I like to consume alcohol and we we're breathalyzed before ascending. Luckily I was below the legal limit. Then I was not allowed to take my camera up. The monkey suit you're forced to wear has many attachments to prevent you from dropping anything into the working bridge (logical) but still they don't allow you to attach anything personal other than your sunglasses. If they attachments are on this suit, you should be allowed to take cameras up but instead they make plenty of money from selling you photos. The tour guide was fine, but i'd much rather hear history of the bridge/Sydney vs. the famous folks you've met on other tours. For the amount of money we paid between the entry fee plus photos, I think it's way overpriced.
At first I kind of hesitated because of the price, but it is definitely worth it. We were provided with a jumpsuit to wear over our clothes that included secure attachments for sunglasses, hat and headphones to hear instructions from our climb leader. We were set up with a belt with a safety line to prevent any possibility of falling so even a person who is nervous about heights (like me) would be comfortable. Lots of photos taken along the way (available for purchase at the end of the climb), great views and information about the history of the bridge and its construction.