Infill on other than every layer does not work.

One of the features that first attracted my group to slic3r was the ability to do infill every other layer (or less). This allowed finer outer layers while not delaying print speed very much. Worked great and we used is on almost all of our prints.

Unfortunately, this using this capability now leads to a nasty bug. If your part has slanting faces, or various other sorts of "interesting" geometry, then any rate of infill, except every layer, causes extra infill to be added to layers that should have none. This causes plastic build-up while printing and eventual failure of the print when the nozzle collides with the build up.

This problem is fully described, with examples, here: Slic3r Issue

What experience have other folks had with this? Is it a real problem, or are we doing something else wrong?

I'm getting the same problem. No matter how I tweak these settings, it infills every layer despite having the infill setting configured to 2. Maybe it's a bug in 0.9.7?

There are some pretty major infill problems with 0.9.7. Just try printing a hollow tube, it will print random infills every 3-4 layers where there should be NO geometry. If you print something like a coffee cup, it may or may not end up with some random layers partway up inside the mug as well.