Sisters of Battle is one of those armies that I always said I'd get around to doing. I love the sculpts and love the fluff. I just always had something else that took priority over starting on Sisters.
That was back in the day before Sisters were cast in pure gold. These days I cannot afford to play in that rarefied strata of society, and plans of a Sisters of Battle army are long gone. Even eBay sellers have gone mad with SoB greed. Slop some paint on a single Sisters model, call it "pro painted", and then ask $20 for it; that seems to be the operating wisdom these days.
Were it not for the generosity of a friend, I would not be able to show you my new and tiny collection of Sisters.
I will use SoB in skirmish or scenario play 40K games. I can add in an Inquisitor and some Imperial Guard to round out things. Honestly, I'll probably draft them into service for other non-GW games. I'm already thinking of other meanings for their iconography and gender bias. I can shove them into some 5150:SA games. I'll find a way to make use of them and have an excuse to get more of them.
However, I won't be buying Seraphim models. At $14 per model, a "codex legal" squad costs $70. That makes Seraphim the one of most expensive squad in 40K. I really have better things to buy for that price than five models.