We've recently re-adjusted our sprint length to be 3 weeks, down from 4. The reasoning behind this was to allow us to align with sprints on other products, to give us a uniformity of scheduling and to permit inter-product developer swaps from sprint to sprint, if needed.
One of the side effects is that our planning process now takes up proportionately more time of the sprint and so the actual work time of the sprint is quite compressed. Couple this with a handful of developers being out for personal reasons (wedding, health issues, impending birth of a child) and suddenly this sprint had a lot of high priority sprint backlog and not a lot of available story point capacity on the teams.
But then something magical happened--what I'll call the "crucible moment." The status of the sprint was that there were a bunch of high priority, smaller maintenance tasks (cleanup of existing features, releasing the previous sprints' work to production, etc.) and then one big new feature. As the teams were working their way down the list of user stories and filling up their story points, everyone quickly realized that that big new feature might not fit into the sprint.
With the purifying fire of timeboxing (forgive my overly dramatic metaphors here), the sprint teams and product teams immediately began self-organizing and negotiating. No one wanted to have a sprint without a killer feature, and so the horse trading began. Some of the higher priority stories were off the "tech backlog" -- non-functional investments in build infrastructure, etc. Developers began identifying tech backlog items that could stand to wait. Product owners began reconsidering some of the higher priority smaller stuff, conceding that some of them might not be so important after all. Different development teams tried to juggle stories between themselves so that the large story could get onto one team's sprint backlog (we prefer not to split stories across teams, to minimize cross-team dependencies). Some stories were scoped down to take less time.
And then, when it was all done, we discovered there was enough room for two pretty big features.
This was scrum at its best--focusing on the art of the possible to squeeze as much as possible into a fixed amount of time. No time for extraneous explorations, just a focus on extracting the maximum product value out of the available resources, with a brutal willingness to critically re-examine priorities. What's more, it was carried out in a context of teamwork between the product owners and the teams; everyone was trying to figure out how to get those features in.
So, a great day for our product and for our organization. We might actually be getting the hang of this scrum thing....