There are a couple of things on that list I'd niggle with.
* Single vs multi-track. Personally I like both kind of events depending on the what and why. You get a lot of energy by everybody being in the same place. Equally sometimes there's a lot to be gained by splitting things up so people can explore different ideas then come back together again. You can use multiple tracks to get folk to think about different things - then come back together to cross pollinate ideas. It can be very energising if done right.
* 30m or less is just wrong as far as I'm concerned. You can certainly have an excellent event that just has 30m or less talks - but that's going to exclude some topics and some methods of presentation. So you need to be aware of that. Instead I'd phrase it as make sure to get the right length for the content. Push presenters hard on how they're going to use that time. Sometimes you'll find that 90m workshop is better as a 10m lightning talk. Sometimes you'll find that 30m talk is better as a 90m workshop.
Other random tips that I'd add in:
* Think about accessibility issues for those with wheelchairs, crutches, etc. and stick something in the publicity about it.
* Provide space for socialising during the event. Not everybody will have the energy or the interest to go to every session. Have somewhere for them to hang out and talk.
* For tech events especially - have caffeine available mid-morning, lunchtime, and mid-afternoon. People need their coffee/soda fix. If they can't find it onsite they'll wander off to get it. Keep people at the venue.
* Plan for smokers. Some people smoke. Make sure you know where they should go, and how to let them know when the next sessions are kicking off.
* Give some space for people to decompress, talk and socialise between sessions. Schedule in more than change-over time between sessions. Allow space for people to get up, stretch, and talk. They come back with more energy and enthusiasm.
* It's impossible to please everybody. Whatever you do some people will like some things and hate others about how you structure an event.
* Follow up with attendees after the event. Try and figure out what worked and what didn't for next time.