My approach is that if it chooses the right index for me, it's up to Domas or someone to fix it if he sees it's broken on MySQL 4. :)
the problem is that API developers add more and more various dynamic query building features, and we hit problems far more in API, than in regular code. Our regular code is just following well known usage patterns, whereas API allows to invent them, and we end up hitting bad index. Today some API logging table queries did overload few database servers. If I really have to go and fix API code, I'll do it with axe. :)
Anyway, FORCE INDEX is needed, when WHERE condition doesn't provide any(/much) selectivity, compared to other indexes, but using index would provide good ORDER BY .. LIMIT optimization.