I have recently discovered Silverstripe and love it, especially how uncomplicated it is. However, at this point in time, I won't be using it due to what I consider a glaring oversight - the inability to have hierarchical / semantic URLs.
I'm sure I don't need to go in to how important hierarchical / semantic URLs are, especially for user experience (remembering a URL, knowing where you are in a site) and for SEO, however I will express my surprise and disappointment at the lack of support.
I'm sure the developers will be able to justify why they don't support hierarchical / semantic URLs but rather than hiding behind some technical reason I encourage you to take a positive view and look to overcome any of the challenges and to address this issue.
Given how important hierarchical / semantic URLs are, I'm sure that I'm not the only one that would be seeking such functionality nor the only one not using Silverstripe specifically for this reason.
Keep up the good work.