These are totally based on my own experience and may not make sense for everyone but:

- In the main projects I'd be working on, how many new files are necessary to consume data from an outside source (say JMS) and log the result.

- What is the frequency of your releases

- How long does it take for a minor feature request to make it from initial conception to delivery to the user

These aren't actually specific to a startup largely because I haven't been burnt by a failed startup. YMMV