I am involved with a project using Visual SourceSafe. We do not have multiple checkout enabled. I will admit up front that I don't have experience with multiple checkout in VSS, but I do in manual checkout systems and it was a major headache. I recall times when an error that had been fixed months earlier suddenly reappeared because the fix got "removed" by a subsequent checkout.
I know that there are comparison features available, but I don't want to have to depend on another developer who is not familiar with my changes to decide what stays and what goes when he checks a file back in when we both have had it checked out. The obvious tendency is to value your own changes over someone else's.
I also recognize that if he waits until I check it in, then checks it out, the same thing can happen, but it is much less likely and a whole lot harder. My experience tells me that I stand a much better chance of retaining my work if only one persone can work on something at a time. I know it's inconvenient at times, but I prefer that to the alternative. BlackburnKL