IntelliJ based browsers haven't been slow in a long time, but they're even faster now, just be sure you exclude node_modules and library directories by right clicking them and things will move pretty quickly.
Web IDEs are fun. The IDEs satisfy a subset of users' need to try something new built on technologies they're familiar with. They might feel warm and fuzzy hearing certain buzzwords that describe the project.
But when it comes to getting shit done and having features that developers and companies will pay to use, JetBrains' and Microsoft's IDEs are the only ones to even come close to being real professional grade tools.
Yes, those options exist. They cover basic use-cases well, but come apart at the seams for others.
tl;dr: Add "editor.zero.latency.typing=true" to the "idea.properties" file.
I switched from WebStorm (was using v9) to Cloud9 2 years ago and haven't looked back, for most Web Development jobs it makes more sense as you don't have to run a staging server to iterate on projects with clients (just send them a link) and you can collaborate in seconds.
I now work at Cloud9 :) after using it a while I was convinced working online where all your tools work together in the cloud is the future. It's way easier to integrate it with the rest of your work flow when you don't have that desktop cloud barrier.
I appreciate the work you guys do on Ace, it's amazing technology. I've built things with the Ace editor, but it's ridiculous to suggest than an editor that doesn't even edit the files on my computer has feature parity with Webstorm, an IntelliJ IDEA based editor. The PSI based AST system is smarter and better than Visual Studio and XCode, and IntelliJ IDEA is better technology than Apple or Microsoft was able to come up with for their own platforms. The number of plugins, the built in features, the fact it runs on my own computer make it unquestionably better than an editor that runs in a browser.
You disservice to a great web editor by suggesting it's better than a native editor like IntelliJ. I write front-end code for a living and in no shape or form would I ever want to use the Ace editor when I didn't have to. It works for sites like CodePen, GitHub and jsfiddle when they're needed, it doesn't replace writing code on my own computer.
However, this exemplifies why I find it hard to use web-based IDEs regularly.