I bought my 610 in the early 1990's and I still shoot it quite a bit, and have owned a 310NG. I really like the 10mm/40S&W in a revolver. I have always wanted an L Frame 646, but they are sky high, and can have some issues with the cylinder from what I read.
I picked up a second 3" Adjustable sight GP100 in 38 Special a while back with the plan of sending it to Clemends for the 10mm conversion.
I sure hope that Altamont gets the Letts Compact GP100 grips in production soon.
I have their Full Size Grip on my Blued 6" GP100. I really like the grip, and they look very good, just too large for concealed carry for me.
I have Pachmeyer Compact grips on both of my 3" GP100's. I managed to come up with 2 sets of New Old Stock grips over on the S&W Forum a while back. Pachmayer needs to get the Compac Grip back in production.
I am sure anyone with a GP100 conversion to 10mm/40 S&W would be happy with it. Whats not to love, a Great Revolver and a Great Cartridge in the same package.
Bob