I'm somewhere between "don't mind" and "avoid". Using tabs in my free software causes me to get a steady trickle of confused mail from people who have loaded it into an editor which interprets a physical tab differently from the standard (notably Visual Studio, which AIUI can be configured into sensible mode but not per-project), and also I sometimes find it actually inconvenient during editing because tabs make complicated editor macros less predictable. So I quite like no-tabs as a policy. But I haven't adopted it yet, mostly because detabbing all my existing source would be a tedious and annoying job with plenty of scope for messing things up and would also have unhelpful effects on things like "svn blame".

Work enforces a no-tabs policy by automatic detabbing at checkin time (and you have to specially mark each makefile as exempt from this when you create it). This is surprisingly infrequently a problem, and generally seems to work well for everybody. (Though I don't think I'd go that far myself, although I might be tempted by refusing a checkin that contained an unsanctioned tab.)