I'm wondering if anyone here has real experience with node-webkit, I'm looking into it to implement a desktop offline version of my app but I'm not sure if their offline DB layer is capable of handle data in the hundreds of megabytes order.
you may ship your app with any database you want. Easiest to use is a pure-JS datastore, like https://github.com/louischatriot/nedb or sqlite. I prefer NeDB, it should work just fine for <= 1GB of data.
If you want to use a non-embedded database, you have to build your own installer, though.
The solutions offered by the chromium part (localStorage, indexedDB) could be worth a look, too. But i have no experience with them when using bigger amounts of data.