I am. Basically, the doctor makes a small incision into the location you choose from a select grouping of spots—I chose my rear end under the bikini line—takes a bit of the tissue out to make a hole, and then inserts the pellets. At first, absorption rate is pretty quick, so I think my first year or so was getting them refilled every three months. After a while, the absorption rate slows, and you can go longer between sessions. I'll be three years on come next January, and at this point I'm running at six months between refills. Every time I get them, it's $330 out of pocket for me with the doctor I go to.
The doctor will make the incision and use the same area every time, but at a certain point, they'll have to move on to a different location. Because you're cutting, healing, cutting the same spot, after a while you'll have small but noticeable scar tissue there (I'm not sure how much it'll go away over time). The worst part pain-wise is the initial anesthesia shot, which stings like a bitch. It takes only a minute or so for the shot to kick in, and once it does, I can feel the doctor doing something, but there's zero pain.
Personally, I recommend it for anyone who can afford it. It's the most affective form of estrogen (from what I understand), and super low maintenance. Hardest part is that I have to take low-level antibiotics for a few days after getting them put in, and keep a fresh bandage covering up the area of insertion for 5 days until the wound is healed and the surgical tape is ready to come off.