Vintage Glamour: I use a lot of the CAS items, like the gowns and tops. The globe bar is a staple for pretty much all my households, especially those that don't have enough room for a proper bar. I also use the white vase with the pink flowers a lot as well as the tray with the cosmetics. I haven't yet had a household whose vibe matches the rest of build/buy, but I like most of the pieces. I just hardly ever use them. Also, I have never tried the butler because so far, he wouldn't fit in with my households.
Backyard: Love that one for its build/buy! I have this one household living at Hound's Head in Brindleton Bay, and their back garden is full of stuff from that pack - there's a water slide (the one with the shark), wind chimes, butterflies, some of the furniture (dining table with matching chairs), the tray with the drinks... and most of the stuff can be used indoors as well, like the fairy lights or the trays.
First Fits: Has some very cute stuff for kids; I especially like the outfit with the backpack and use it a lot. Plus, most of the clothes work for both girls and boys.
Country Kitchen: Lovely and matches Cottage Style pretty well, though it has a slightly shabbier and worn look to it. Works surprisingly well with shabby builds - one of my Sims lives in a rather decrepit house in Moonwood Mill (I think New Moon Shack's the name), and the items from this pack fit in perfectly with the overall shabby style of the house.