I did pellets a time or two before switching to shots. I had a pretty good experience with them since the clinic also prescribed arimidex. The pellets will only last about 4 months so you'll be going under the knife about 3 times a year. That's a lot of cutting and stitching you'll be looking at over the years. The down side for me was the expense.
Way more than I wanted to fork out, but if insurance covers it, then maybe not a bad option. People comment about not having any control over their numbers once they are implanted, but I'm sure they will get you locked in pretty quickly. I had to go back and have a few more put in after the initial ones. The big issue might be the endo's knowledge and experience and whether he can and will get you dialed in with ideal numbers.
I did like not having to worry with anything after they were in place. Your backside will be a little sore for a week or so. Say you do these for life... That could be another 50 years multiplied by 3. 150 times to get sliced and stitched (actually I think they glue). I remember you had to keep that dry for a few days until it began to heal. There will be a small lump where those pellets are that gradually reduces in size as they are absorbed.
I'm happy to do shots now. Subq with tiiny 31 g needles is easy. And that's coming from someone who hates needles.