I know what you mean, I would use bugles a lot more too if it weren't for the risk factor! Some are sharper than others - but it varies from batch to batch so I can't really generalize. I've never resorted to filing the ends (life's too short) and I really hate Fireline (I like my beadweaving slinky) but I have had some success with putting seed beads at either end, and I'm just very careful about where and how I use bugle beads. I try not to put them anywhere 'structural' (such as the intersections of netting), but always try to engineer the piece so that the thread is passing straight through them and not coming out of the ends at an angle. Fringing is ideal (a lush fringe with those twisted ones is fabulous) and they are good for embellishments where the thread isn't taking the strain (such as diagonally across a big right angle weave trellis). I tie lots of 'just in case' knots when I'm using bugles, so if they do slice the thread I only lose a little bit of the work.
PowerPro is a bit more resistant than Fireline, but it's quite thick, so you wouldn't want to use it for everything... might be worth a try though.
Having said all that, I have a random peyote collar with all sorts of bugles, stone chips, diagonal cut beads, sweepings, you name it... I've worn it lots, had it several years now, it's on ordinary polyester sewing thread and still going strong, so maybe I'm unnecessarily paranoid!
My website: http://lynndavybeadwork.co.uk/
I wondered that when I saw that bracelet too... but it must be a good technique as there are several versions illustrated! I would never have dared to make a piece like that. Yes, please tell us what the secret is!
I use bugles with Nymo D all the time, for fringe and in free-form peyote bracelets, and netted pieces. I always use seed beads on each side of the bugles, and I've never had a problem with the bugles cutting my thread. Maybe the secret is the brand I use - if so, you're welcome to it. I use only Miyuki bugles, and I pick out any of the broken ones before I begin the project. Miyuki bugles are a little pricier than your average bugles, but I think they're worth it, considering that I've never had a problem with my work falling apart due to cut thread. Good luck - I'd be interested to know if you ever get bugles to work for you.