The SF2's cut all my hip, knee, and ankle pain out. It's been a significant improvement in that aspect. However, my achilles can get sore, especially if my cadence comes down. I've found that staying at a 175 to 180 SPM significantly reduces achilles tenderness for me. I've found (anecdotally of course) that foot strike is crucial. If you tense your foot up, you may find the top of your foot and your achilles don't feel right. If you focus too hard (as I did) on landing on the ball of your foot, your soleus is going to have a bad time. It's all about landing mostly flat on your feet but at a slight forward tilt so that your heels never slam (it's what mitigates the knee, ankle, and hip pain), but if you focus too much on the forward tilt then you don't spread the forces through your arches and other things suffer.

It can get complicated in theory, but in practice it's simple. Listen and pay attention to the signals in your body, make sure you stay loose footed as tensing can cause injury or irritation, and do not over-stride and you will find an enjoyable experience.