I love SW. :) When we started homeschooling DD used Spelling Workout. She's a fairly natural speller, memorises things easily, and found SWO to be a waste of time. Switching to SW was the best spelling decision I ever made. :) Both my natural spellers (I've got one who's finished SW and one just starting) and children who struggle more with spelling (one finished, one part way through) have found the dictation passages very enjoyable. The programme is very flexible, so we're able to jump around between levels without a problem.
While spelling rules are not explicitly taught, they can still be learnt. For instance, while learning the word "notion" I might ask DC, "Can you think of any other words which end '-tion'?" Sometimes my kids have pointed out spelling rules themselves which is really great.
Another thing I love about SW, although it's probably not an issue, is that there is a British version. As you can probably tell from this post, I use British spellings and have no intention of changing. :D
If you have any questions, feel free to ask me.