I don't know if this was in the guide or not (I didn't see it), but once you can afford it, coffee makers are quite valuable, particularly for hacker sims.
Here's how coffee works: when you drink a cup of coffee, you get a 3 hour "buzzed" moodlet. This does two things: for one, it gives you a 30+ mood boost, for two, it removes any "tired" moodlets you have.
There is are drawbacks however. First, you cannot go to sleep during the "buzzed" state. Additonally, after 3 hours, you will get a "crash" moodlet, and any "tired" moodlets you have will come back.
Most people know this, however the thing is, if you drink coffee every 3 hours, you can permanently stay in the "buzzed" state, meaning you will have a 30+ mood boost, and you won't have to sleep(although your energy bar will still deplete).
This is ideal for hacker sims, since you can only hack at a certain time, and it's tedious to time your sleep just right. You can set up a "coffee station" beside your computer and stay up through the night.
Unlike the moodlet manager, this effect is quite balanced. For one, you still have to take care of other needs (food, bladder, hygiene, social). Additionally, you CANNOT take coffee in you're inventory, and you have to drink more every 3 hours, making it extremely impractical to do certain things, such as fishing or gardening.
When living off of the "buzzed" state, your sim will be almost entirely homebound. Additionally, there is no way to maintain the "buzzed" state if your sim has a "normal" job as the effect will wear off halfway through the day.
I'm not sure where you'll want to put this information. I think it certainly has a place in the self employment guide under "hacking" and in the "tips" section, but it's your guide, and you know what's best.
Hope I helped. =)