I think the fact that they do a week devoted to reducing technical debt is just as awesome as the WOW week (and giving the innovation time right after code improvement is probably the best way to do things.)
I'd be concerned, though, that having an "innovation week" only once every 2 months might slow down whatever momentum you were building on a project. I know I'd want to keep plugging on my 12.5% project after hours in between the chances the company gave to work on it. Which might be exactly what they're hoping for, I suppose.
This is a great concept, although I share a couple of the concerns mentioned (project momentum, and the implied issues with this technique as the organization grows).
I recently highlighted that I'd like to have a pot of opensource days that I could use at my discretion (http://imperialwicket.com/how-about-some-open-source-days). I think it offers a similar benefit, while maintaining a lot of personal responsibility for timing and usage. That said, the structure of WOW week has a lot of built-in benefits as well (team-building, motivation that comes with working as a larger unit, etc.).
Nice job, PatientsLikeMe. It's good that this type of insight is being pushed and highlighted as a productive technique both for the organization and the employee.
I've worked at a company that tried to implement these types of 'hackathon sprints', but it always came down to last minute fires or upper management delaying them at the last minute for arbitrary reasons.
Glad you guys are able to do it, and I hope you'll continue to do so as you grow.
We rotate one person on 2-week interrupt-driven bug duty - we do have bugs we have to address immediately, but the interruptions are constrained to one victim. This helps protect the rest of the team.
We also struggle with bleed-over and follow-up work from a previous development sprint when WOW Week comes right afterward. There's no silver bullet to prevent this, though we try to be more disciplined about letting work slip if it can't ship completely on time.
We do this at Top Hat Monocle too, except we call them Hack weeks. We've found it tricky to make sure they are respected, meaning it's hard not to get distracted by critical bug fixes. We have quite a small team right now so that might play a part in it.