<p>I want to implement Scrum, but I can't decide on a Sprint length. Ken Schwaber seems to relate that 30 days it the defacto... but I can't imagine waiting 30 days without the possibility of changing direction or reprioritizing. </p>

<p>Our projects usually only last 1-3 months using the waterfall method and moving to Scrum would probably mean less opportunity to fine tune.</p>

<p>I was thinking about 1 week sprints, but this seems like Scrum Micro Management.</p>

<p>Having 2 week sprints would probably be ideal, but I want to know if others out there were able to implement this successfully. What are the downsides? Is it more work/less work/same about of work to manage a team with shorter sprints?</p>

<p>BTW... 3 week sprints seem odd to me, who does a 3 week sprint? Why not just make it 4 weeks. ;)</p>

2 weeks (10 standard working days, if you are a M-F outfit or 12 if you are a M-S outfit) is half a month (a month typically has roughly 20 working days in it, give or take). Also, week is more vague than day but less vague than month, so it makes the unit of measurement in weeks better for more agile (more give/take) development projects.
However, the last time I did anything like scrum, it was on a school project and it wasn't truly scrum. So it was 7 day weeks in a 10 week quarter. I really liked the 2 week block for that situation. I felt that I could get a lot done but we could adjust timelines and plans frequently.