The I61 is my "go to" 50mm. I love the sharpness and contrast. I'm waiting to get the first roll shot with my new Jupiter-3 back; we'll see if I still feel the same after that!
I'm awaiting my first roll back with my bessa-r and I61. I also just got a j-3 (from Yuri) and I got some shots back yesterday, I only took a few with it, but they came back great. It's a nice lens.
I feel like my I61 is a little softer than the j-3, it has a great feel to it. The j-3 is more versatile. Which I take with me will probably depend on conditions.