If I'm not mistaken, a number of people use them at the range for HP competition, but I think beyond 200yds (300yds on a good day), most people shooting less than .30 cal don't count on seeing the bullet holes in the black unless they have some serious glass, or the lighting is just right. Not just the 50mm Kowa's, but most of the 'budget' priced scopes, i.e. most that cost less than say a Kowa 661 or 821M. There's probably some eagle-eyed fellow out there that can see .224 bullet holes in the black at 600yds thru a Bushnell, but for the rest of us...
I'd say if it fits your budget, it should do OK. From the research I've done trying to find a 'budget' spotting scope, I've pretty much came to the conclusion that the Kowa's are the only game in town if you want LER. After that, the Nikon Sky & Earth 60mm w/ a 25x WA eyepiece (~$290) or a Meopta 70mm w/ 25x WA eye piece (~$350) are probably good choices. Some folks have had good results w/ some of the Chiwanese TSN-1 clones like the C-Star from the Sportsman's Guide or the Raven from Eagle Optics. They come w/ a 20-60x eyepiece, but apparently will take a 25x LER eyepiece for a TSN-1 or 661 if you can find one for a reasonable price on e-Bay.
I've about had it w/ my little 15-45x Bushnell Birder straight tube scope. I've beat the tar out of it, as it was meant (by me) as a 'carry' scope. Still has an amazingly sharp image. I've just got to the point where I want to be able to look thru the scope while in position from prone, and that's kinda hard to do w/o an angled eyepiece. Not impossible, just uncomfortable. One of our local Hunter BR guys has a Meopta scope and just raves about it. The few times I've looked thru it at the range it did seem pretty sharp, so I'm looking real hard at that 70mm Meopta. Not their 'better' 75mm model, cuz for those bucks I'd be getting a 661 or 821M Kowa!
Well, hopefully I helped a little w/ all that