I've never used a formal spelling curriculum, and I was incredibly frustrated by weekly "spelling tests" when my kids were in primary school.
DD1 is a naturally good speller. She didn't need any of the lists.
DD2 is a naturally horrible speller. Memorizing 10 words a week did NOTHING to help her spell better. She quickly forgot the memorized words. She does tons of reading, and has a good general sense of how words should be spelled, but she often forgets to double consonants or mixes up vowels. Her spelling is 100% comprehensible, even though many words aren't spelled properly. What's helped her spelling the most has been typing on the computer and then running her work through spell check. It's not JUST that spell check catches her mistakes: by seeing the words she misspells pop up like that, she's actually learning how to spell them!
DS has an innate interest in spelling words correctly. Tthis is partially fueled by Webkinz- that website has a list of words that are acceptable, and if you put in any "bad words" or misspell anything (so you include any words that aren't in their dictionary), it won't let you submit what you've typed so others can see it. He's constanly asking me "Mommy, how do you spell ______" (and has been doing that for years, even before he did much typing on Webkinz). He still does that-asks how to spell something when he's writing or typing, no matter what else I might be in the middle of when he wants the word.