A general assessment:
Power Weapons
~ as noted, a power sword took a slight hit. AP3 is still not bad, but it can be annoying when terminators come to call.
~ The power axe is definitely worth a look. Firstly, for those who give a crap about background, the Axe of Chalcydon (or Axe of Retribution) is a canonical sisterhood weapon. Secondly, unwieldy isn't a big deal for a (generally) hard to attack character, and S4 (S5 for celestians) is a nice one.
~The power maul is something we have an existing model for. Don't knock S5 against non power-armoured armies! Being able to wound a warboss on a 4 and still ignore eavy armour is very nice.
~ Note - the FAQ SPECIFICALLY opens 'power sword' up to 'power weapon'!
~Death cultists suffer but I can't really make myself concerned as they were *&?^"!!! broken as hell anyway.
~Crusaders with an axe match some of the artwork, look bad-ass and are very effective.
Meltabombs
~ seriously, just yes. S8, AP1, useable against walkers at full WS and now against monstrous creatures too. Don't knock massed krak grenades either.
Overwatch
~ Bolter overwatch isn't a big deal as 6's means not so much from small units. Footslogging units of 20 girls, however, hurt like crap, especially with paired flamers too.
Characters
~ A character in a squad can only be realistically picked out by another character, even in combat. This makes priests VERY tempting, especially given the above footslogging squad of mobile rapid firing death.
~The eviscerator is a power fist with armourbane. Dual-wielding eviscerators is still a go.
Seraphim
~ Yup. They're even nastier now. Jump in, fire 4 hand flamers, Celestine's ardent blade, 14 bolt pistols and the superior can lob a frag grenade in for giggles. All rerolling to wound. Then, you charge, and get impact hits before the fight starts. Then, assuming they had some mates nearby, if they charge you, you get to put another 8-ish automatic hand flamer hits, 2-ish heavy flamer hits and a couple of bolt pistol hits before the fight starts!
~Celestine confers fearless on the unit she joins. The Seraphim confer Hit and run on any character joining them. It's a match made in infantry-murderizing heaven.
Transports
~No charging out of transports is irrelevant - for sisters they tend to be hoiksing gun-units around anyway
Exorcist
~ Weapon destroyed is random. That means, for the price of a pintle-mount, you have a 50% protection for the exorcist launcher against your first weapon damage. I say worth it!
Allies
~ Faithful characters (i.e. a canoness) can pass on 'the passion' to allied battle brother units. Equally, 50-man combined guard platoon led by uriah jacobus, or additional awesome leadership guard characters (like yarrick) to boost the army's resolve up close.