I like some of their candles and don't like others. I love Spiced Pumpkin (even though it's not exactly sophisticated and maybe a bit loud), Buttercream, Christmas Wreath, Mistletoe (does anyone else get a kind of 'fungal' note there?), Sage & Citrus, Greenhouse, and Balsam Fir (I think it was called that--it was discontinued, I believe). I don't like Wedding Day, a lot of their rose scents, and many of the new ones. Also, their Leather car air freshener is second-to-none in the category.
I loved going into the stores and checking what they had when I was able to. But since I live in Sweden now I don't see Yankee Candle much. I run into some of their new offerings a lot at certain stores, and those are nearly always disappointing. It seems like they're always trying to do a tropical drink fruity thing, a vanilla+musk thing, some other cupcake type scent, and maybe a trendy floral, and a lot of those either don't work or smell like they were conceived in a focus group, designed for wide appeal to a profile of a customer. And they smell like they have a dime-store budget. It's also disappointing to me that they end up discontinuing a lot of the scents I like best, like Balsam Fir, Greenhouse and the various green grass-without-dominant-floralcy things. I also wish they'd try to be a bit more daring with their seasonal scents instead of always doing a variation on apple for autumn and vanilla or pine or cinnamon for Christmas. That said, they have one out this year that smells vanillic and soft musky to me--I think it's called Snow in Love or something? That's quite nice.
As for the candles and tarts, I've pretty much always been pleased with the amount of smell they give off (is this the 'bloom'?) and the burning time. I think I'd like them to update the design of them a bit. The room sprays don't work as well for me. There's usually some kind of off smell there, and maybe it's the propellant, because I've noticed the same thing at Bath and Body Works.
And speaking of BBW, I really like their candles by Henri Bendel. I find those superior to Yankee Candle, but they're rather expensive. At least with YC, you have a HUGE selection and can mix and match and have fun with things. Especially the tarts. Love the tarts!