I'm a brand new beekeeper this season, so my expierence isn't extensive, but I have SBBs on both my hives, elevated on cinderblocks. Even though we've had a cool rainy summer, both of the 4-frame nucs I hived on June 23 ramped up very nicely.
They started on foundation, of course, and have drawn most of two deeps and they're hard at work on the goldenrod flow we have now.
I did put on a solid bottom board under the screen to do a mite drop test. After a week, even with tilting and an upper entrance, there was moisture on that board. So I think the screens work better, and I'm going to leave them on all winter. From everything I've read, it isn't cold that kills bees, but moisture, so it makes sense to me that the SBBs would help with that problem.