KK - I've made this a few times and highly recommend making it according to the recipe and see how it works for you. Meyer lemons, as noted earlier, have a different flavor profile than "regular" lemons, and using regular lemons could determine how much sugar you use.
Also, I made it once using regular sugar, and there was a very slight graininess the result - not as smooth as when I made it other times. I believe that the sugar did not dissolve as well as it would have had superfine sugar been used. So, if using regular sugar, be sure it dissolves completely - you may want to cook the syrup mixture a little longer than what may seem necessary, although you seem to have been satisfied with the texture.
I am convinced that some yogurts have additives that can effect the result. I made it a point to check the ingredient list on the yogurt I used to be sure it wasn't "contaminated" by odd ingredients. It's also possible that the results might be a little different because of the type of yogurt used: fat free, low fat, full fat. I'm just supposing on that point because I've not tried a side-by-side comparison of the three possibilities. However, I'd strongly suggest to anyone making this dish, use a good quality Greek style yogurt.
Finally, I made sure to finely mince the lemon zest, and let it sit for a bit in the hot sugar syrup mixture before adding to the yogurt. That gave a smoother texture and mouth feel than when I didn't mince the zest so fine, and letting the zest sit a bit in the hot syrup may have added a bit to the lemon flavor.
Regardless, it's an easy and tasty dessert to make, and in some ways, using yogurt makes it a little healthier than panna cotta made with all cream. I'm glad you liked it.