My 5 yr old tends to reverse his letters, but I blame part of that on me not overseeing him everytime he's writing something, which happens because while I'm busy teaching the basics to my older 2, he busy's himself with lots of drawings and loves to "write". The most obvious was seen recently with a picture he drew of a superhero saying: "murhtabeht".
Now, at first I didn't have a clue what they said, but start at the right and he was actually writing very well phonetically "the bath room".

Now I don't exactly know what to think of such backward writing, except that perhaps he'd prefer to learn Hebrew as a foreign language, since it's written from right to left. And I was surprised that he didn't reverse any of the letters, which he usually does. But I've started working with him some having him practice his letters on the chaulkboard, and I plan to continue that thru the summer. But I really feel I'll just need to stay on top of it for a while so he doesn't slide into his old habits.
As far as ETC is concerned, I use an Orton-Gillingham method for phonics (SWR), but I've had my kids do the ETC books and they actually like doing them. We started with the A/B/C books in K, mainly for practice with writing their letters, but we continue doing books 1-8 mainly for phonics & reading practice.
For a short while I switched to Abeka's Letter's and Sounds, because they have nice colorful pictures, but they were getting better phonics & reading practice with the ETC books. With Abeka's, there were some exercises they could do by rote by just noticing a pattern but not really reading anything (circling special sounds, for example). With ETC, they have a few similar-looking words or sentences which they have to read carefully to pick the correct one that goes with the picture. ETC books have very simple instructions and are quite effective, imo.
hth,
Teresa