We @ medicware.com.br are thinking about making our web application offline-capable with Gears. Our main goal is to keep basic functionality running when the internet connection goes down.
So, I'd like to hear success stories, tips and resources about yours real experiences in that field (related to Gears or not).
Remember the Milk has done a nice job of using Gears -- you might see what you can find out about their implementation. I'd start at http://code.google.com/apis/gears/articles/take_app_offline.html.
I've had good experiences with Adobe Air. It's not gears and it was nothing more than a look to see how it worked, but it was so simple that i'd think it would be easy to port any large scale application over.
Do you have to use Gears? I've used their AdWords API extensively, as well as Google Data, and the experiences left me lacking. Sure, things are reasonably well documented, but when it comes to support, there's no one you can call and real Google developer postings in forums are rare. They also are known for announcing cataclysmic changes with little notices, and, this is on paid products like AdWords.
I'd seriously look at Adobe Air. Adobe has worked with 3rd parties for years and they're pouring tons of money into doing Air right.
There is a couple of video resources available:
Dion Almaers 50 minute presentation goes from overview/businesscase down into the actual code: quite helpful for understanding concepts and getting examples for actual implementation code. Offline web apps with Google Gears
I recently saw "Google I/O 2008 - Taking Large-Scale Applications Offline". Good for grasping the concept but also very complex -- Googles problems are most likely not typical scaling problems. And there was no concrete code. Only some architectural strategies.
Also, if you need code examples, try "offline dojo" as well. Even though it's a screencast of Dojos offline wrapper, I think it's pretty helpful (and only 8 minutes short) Dojo offline screencast, (overview on dojo offline homepage)
In my eager to answer your question, I just stumbled upon Google I/O 2009 - HTML5 Databases/Gears & Offline Web Apps, which i will see during lunch. Feedback on this yet, anyone?