Downloaded app can be used offline.

But the question is: is that really important to the majority of the users who download it? Or are they acting blindly?

Now, it could be that there is a contingent of bingo-loving teachers who absolutely prefer to have the software locally installed, but I'm suspecting (without any good evidence, I grant) that this is not really a key decision-factor for most of Patrick's customers who choose to download.

I believed for years that there was a group of customers who would pay for downloadable versions when they wouldn't pay for web versions. In fact, I put AdWords ads on many free web-based competitors, and those are my best performing ads anywhere.

But I've come to believe, after listening to customers and seeing the behavior in tests where I emphasize or deemphasize the options, that this doesn't say that users want to use downloadable applications. It was just that users want easy to use applications that don't suck. Next to the free web apps in 2006, BCC downloadable was easy to use and didn't suck. Next to BCC downloadable, BCC online is easy to use and doesn't suck.

I'm not paying to use the web version, but if it's written in HTML5 it can leverage the cache-manifest (or Gears, either way) and work offline as well.

Do you know one way or another that it isn't?

Unless HTML5 has some previously undisclosed way of running ImageMagick and Prawn, I'm going to go out on a limb and say that this will not work offline that well.