What prompted this: In the new WD there's an article revamping Assassins a bit - most importantly, including a good bunch stratagems to use with them (mostly stuff like letting a Vindicare shoot twice, letting an Eversor fight twice - but maybe take a mortal wound - that sort of thing), but one of them is huge:

That's 1 CP to set aside 85 points (they're all 85 points now) and take a single assassin of your choice at the beginning of the game. It's mostly good because it means you no longer have to give up a detachment to include assassins, as you did previously - and in matched play events (like, say, Nagoyahammer) where your number of detachments is limited that's giving up a lot. It also gives you the flexibility (if you have the models) to pick which assassin you want depending on who you're facing.
Overall it's a nice change, and actually makes taking assassins viable. Looks like WD is keeping it up!