I've spent the past few months attending way too many conferences, and I've noticed a few things that I'd love to see conferences improve on. Here is my list in no particular order. Enjoy.
Skip Slack
I like Slack. A lot. But for the love of God do we need to create a new Slack organization for a conference we'll only be at for a few days? I get that it's an easy way to chat, and it's certainly more user friendly than IRC, but this just seems like a waste of time.
That being said - I'll offer a counter proposal. Someone create a "DevConference" Slack group and just use one channel per conference. I'd join that in a heartbeat.
Skip the Mobile App
This has nothing to do with web versus native (although I'm clearly biased towards web), but again, why do I need an app for a few days? Just build a darn web site that's responsive and works offline. Building a mobile-friendly site should not be a problem in 2016. Offline is not much of a problem in 2016. You can skip the sexy service worker stuff and just AppCache if you have to. Or skip offline support completely. While conference wifi can suck, generally the cell networks run just fine.
Those housekeeping notes
Pretty much every conference I go to starts off the day with housekeeping. Where's the bathrooms? Where's that one room that isn't by the others. What's the wifi password. What time is the social event.
Pretty much no conference ever bothers to put that information on their web site. If you miss those morning notes, you're just out of luck.
Before the conference, your web site is a great marketing tool to get people to your event. During the conference it needs to shift focus to being an information source for folks actually attending.
Misc
A few more random things:
Few conferences make note of the time between sessions. So for example, the one I just left (which was darn good by the way!) had a session at 10:30 and one at 11:30. Speakers were to use 55 minutes. This should have been noted on the schedule too.
Oh - and it boggles my mind that I have to say this, but have explicit time between sessions. I attend a conference earlier this year that had no time between sessions. I don't know what they were thinking.
When you provide food, try to be descriptive about what folks are getting. For example, if you've got a hot breakfast, let folks know. That way I can decide if I want to eat elsewhere.
Provide water for speakers. This is definitely hit or miss for conferences, and partly it is my responsibility as a speaker to handle this, but I really like it when water is provided in the room.