Disclaimer: I'm just a Psychologist with great love for technology. I'm ignorant about coding and UX design implications.
This is meant to be just a simple analysis about two amazing projects and the web computing experience.
Jolicloud is an amazing project that uses Linux, HTML5 and the Chromium technologies to create a cloud based user experience while keeping the access to local stored apps. It uses chromium instances to launch web apps like a regular local app. Additionally, you can use Chromium to surf the web.
ChromeOS is also a Linux based project, built on top of Chromium (which lead to the best browser ever, Chrome: ok, it's my opinion). Its main attributes are speed, security and simplicity.
With the motto (in my own words) "live the web", they are working to give us nothing more than the web. Nothing more, nothing less. Although it sounds appealing, and it sure is, there's no possibility to run local apps. That's the great distinctive point when compared to Jolicloud. It can be a caveat to some people which for some reason need local apps to do their business.
To put it simply, ChromeOS is a Chrome browser with a linux kernel. It doesn't allow you to open that word document or that game that you like to play on your Windows machine.
Now you might be thinking that the hybrid approach of Jolicloud is much more interesting than ChromeOS. If you need local apps, it probably is; if not, the case can be different.
While I really enjoy Jolicloud I think that it has a great inconvenient. Let me TRY to explain. If you want to access a web site in Jolicloud you launch Chromium (or any other browser but let's keep with Chromium). But in Jolicloud you also have the possibility to click a web app, which will open like a regular app. You get Chromium and the web app as two separate apps. This is when things get weird.
You open Chromium and start browsing the web (check emails, read the news, etc), loading several tabs in the browser. But then you remember to open that amazing web app that you found in the Jolicloud "store". You click it and it opens independently of the browser. Now you have a browser with several tabs and a web app. Which leads me to ask why would you have a web app launching as a separate instance and not like a tab of Chromium? On the other hand, everything you open in ChromeOS will be presented in a tab. Every web app will in each tab. That makes a great difference to me.
How do I think that Jolicloud could fix this? Simply by forcing each web app to load as a tab of Chromium. If they do that they will improve the user experience dramatically.
I'm eagerly waiting for ChromeOS. I think that it has the potential to change the computing paradigm. Being an avid Chrome browser user and Google apps aficionado (Docs, Calendar, Reader, Books, Picasa etc), I think that if Google:
a) improves the way apps communicate between each other in the web (e.g., drag and drop between different web apps);
b) introduces integrated offline capabilities to Docs;
c) improves Docs compatibility with Microsoft's documents;
d) improves speed, memory management of tabs and security in ChromeOS;
e) brings movies and music services to the Google apps experience, syncing them with Android's software (both in tablets and smartphones);
f) convinces carriers and manufacturers (e.g., LG, Samsung) to provide Android's firmware updates without having to rely on Windows or Mac software;
g) makes it clear to customers all over the world that ChromeOS is not an evolution of Windows or OSX but a revolution in the way you interact with the web;
h) keeps stimulating developers to create great web apps (e.g., with HTML5 strengths and other web technologies); and
i) ensures that vendors will provide well designed hardware (notebooks like the Cr48 but better, and other appliances like TV's) at a good price.
If they do this they will have great chances to change considerably the computing experience of millions of people, benefiting Jolicloud and other web driven linux distributions with their success.