Summary: Years ago I used an older version of the lensbaby. It was cool, but not exactly easy to use. This one is a lot more ergonomic, and easy enough to hold the camera with one hand, and focus the lens with the other. It takes a little getting used to, but it's not a steep learning curve. I think it's a pretty decent value for the price. I use a Canon EOS 7D, and shoot manual exposure.
Summary: I have this paired with the Edge 80 optic. Fits and works well on both my APS-C frame camera (T3i) and full-frame (5D Mark II). This has seriously become my favorite setup to just walk around with, supplanting the 40mm f/2.8 STM (which is an excellent walk-around lens, btw). I'm not a fan of the school of "this a great camera because it forces you to slow down and really compose" thought.
Summary: This is the best money I have spent on anything photography related in years! Its a little more challenging to use than the typical auto focus lenses but when you get it right all your pictures become works of art. Just when I was getting tired of my camera setup and getting some new gear lust, the lensbaby lit the "spark" (bad pun!) for some new creativity! Best $75 I've spent in a long time.
Summary: This is a great starter lensbaby lens for your Nikon -- if you are not sure if this is a worthwhile lens for you, its pretty much the "original" and you will quickly be taking artistic shots. THere are better quality lenses now available from Lensbaby, but none as light and convenient as this at such a low price. You'll have fun with this!
Summary: My photography covers too wide a range of styles for the Lensbaby effect to be used more than rarely: still, I like what the company's products can do and was interested in learning how they would blend in to what I envision about selective focus. Frankly, however, I always thought most Lensbaby models were overpriced for what they could be expected to do, so I was delighted to see a truly economical version hit the market recently in the Spark.
Summary: Didn't think much about this item except that I wanted to try an item from LensBaby that wouldn't break the bank. This was that item. For under $80 dollars you get a pretty decent lens to play with. I used it on my Canon 7D and T2si with no problems at all. You can get some great shots from it. I would recommend this for any photo bag. Fun lens to play with.