I would probably be much happier not squashing stuff if you were able to bisect cleanly to points between branch merges. I don't think that's even theoretically possible; which means that when you're bisecting it's quite possible to pick up half-baked mid-branch points that you have to recognise for the broken rubbish they are - lots of false positives there occasionally, and makes bisect a lot less useful. On a repo with nice squashed commits, you tend to be able to narrow down to the feature very quickly - of course those commits then tend to be bigger etc., but I find that less of an issue.