Love the mentions from SB Morgaine & Kassiane!

The CART and transcripts are also great for not only people with hearing impairments or ADHD, but also Auditory Processing Disorder. (I can hear well, but have decoding errors, so it's Mondegreens all day long.) See? Two kinds of accommodations help a variety of different people. Win!

Include a pocket folder with conference materials for people to keep their pages and transcripts. TIP: Put a sticker on the front to remind attendees to put their name on it. That saves you from having to give out so many extra copies to replace those mislaid, and if you get people's contact info (mobile voice/text/e-mail) when you hand them out, then you can let people know when someone else has turned in a lost packet. (It's not just about saving the trees; we have our precious notes on those pages!)

TIP: Glue a [full-page size] copy of the meeting site map on the front or back of the packet, and the schedule on the other. Yes, things change, but most of the plan will stay the same, and there will be less paper shuffling and dropping throughout the day. It may sound like up-front work for something that only helps a couple of people, but in reality, most everyone will find it helpful and wonder why it's not standard.

Clearing out feedback in your sound systems would be fabulous; I have hyperacussis and nearly fall off my chair in pain. (It also triggers the noisier version of my tinnitus, which in turn makes understanding speech difficult.)

Loud background muzak/DJ, disco-ball and/or strobe lights and such are fun for some people, but limit them to a particular time and location [behind doors]. They're migraine-inducing (as well as being hostile to epileptics). BTW, that timing should not be part of the regular dinner event or whatever -- don't make people miss important segments.

Non-smoking everywhere in the event, including outside doorways.

Extra seating for socialising, and seating accommodations would be lovely.
Tables should be at a height for those who use wheel chairs (bar-stool tables are too high). Remember, it's not enough for aisles to be wide enough for people using wheels; there has to be enough room to U-turn at dead ends!

I love the idea of quiet areas. It would be great to "recharge" from getting so overwhelmed by all the lovely input and too much peopleness. I hate having to either have to choose between not being able to focus or remember what I'm experiencing, or going to my room and feeling like I'm missing what I came for.

Lastly, THANK YOU for asking instead of assuming that what you already have must be okay, or that what occurs to one or two organisers will be what the attendees want and need!