I've seen others comment on this, but I have to add my 2 cents. I'm finding that many fonts (that is, usable fonts) common to subtitling are displaying weird, annoying lines that bleed out from the font. It seems M and W are the worst. Basically, it makes the entire caption option useless. My only option is to subtitle as graphics and pray my client doesn't ask for an SRT file. I REALLY hope this obvious bug is worked out ASAP. (Of course, I'd like to mention how the entire captioning section needs to be reworked, but one thing at a time.)
Note there are 2 posts there by staff, that give some background and a workaround. I don't believe that I was ever 100% happy with the workaround, but it has been several versions back that I tested it.