Dave- I know exactly what you mean about these being so much fun. I got the S&W M&P 15-22. I took the sights off of mine too and put on a Browning Buckmark reflex sight (only for air guns and .22s) that I got for something like $40. It has 4 different reticles. But I just use the 3 MOA dot. What a fun way to spend an afternoon. Then just to have a matching sidearm, I bought a GSG 1911-22.
But in an afternoon you go through a few more shots than you would with a ML. I usually end up grabbing a carton of .22s about once a month at Walmart for <$20 for 550 rounds.
That is a very cool looking rifle. I was at a gun show yesterday and almost grabbed a Hi Point carbine in 40 S&W but the guy wouldn't budge on the price. So I walked.