I have one and it seems you'll be limited to the scope you can mount. I wanted to use a Centerpoint 4-16x40 but it's to wide under the turrents (center) so doesn't sit in the rings. I have a Centerpoint 3-9x32 that does fit it and tried it out on my NP XL1100 but that gun needs some work so I took it off. I have a Hawke 3-9x40 AO that is shallow enough but not long enough to fit the rings. Luckily you can undo a set screw and move the rings closer so I may try it with that scope on my Nitro Venom .177. I haven't put in enough shooting time with it to say whether the poi moves over time so it looks like I have some shooting to do.
Pros-
does adjust out some barrel droop, picatinny rail
Cons-
limited to scope size
I wish someone would make a picatinny mount like this:
Beeman 5039 1-Pc Adjustable Mount w/1" Rings, High, 9.5-11mm Dovetail
Have it and it is very nice... have my scopes optically centered and used the mount to get on target.
Greg