Is it worth it?

IMO, yes. 
I own an MKIII model but, I have never used it. So, how can I recommend it? 
I specifically searched for a Hill pump due to their reputation, brand name, and the availability of rebuild kits. The last reason was very important to me. My hand pump is now a 3rd stage backup for filling my rifles. So, it literally gets no use. But, if I ever have to rely on it and it fails, I know that I already have what I need for a complete rebuild. 
Tom
 
I share the night and day opinion so I will give you my perspective as compared to the Benjamin pump since I had both. For one the the Hill has a much better gauge. Although they both do the trick the Hill is much more solid. Next the Hill comes with an attachment to filter out moisture. The Hill pump works with air more efficiently and takes less pumps and effort. At the end of the day it really depends on your budget if you can afford the Hill go for it, if not the Benjamin will suffice. The Hill pump also has the ability to fill to a higher PSI I think it is 4300 as compared to 3600 but don't quote me on that.
 
The hill is so worth it. I have been filling to 250-300 bar, mostly 300, with it and it had held up even thought it red lines at 275bar. One piece of advise. Don't over grease the outer tube or you'll have to do a premature rebuild and it'll be a real mess to clean. Smooth and easy to use throughout the pressure range. It is a workout though.

You will likely need to get a female 1/8" bspp quick connector for it though.
 
"jag159""day and night" How so?
My Benjamin pump came with a gun I picked up so I used it until it gave out. I ordered a rebuild kit for it, then while waiting for kit to come in mail, I found a Hill pump on sale, so I bought it + the female adapter to fit.
I've never counted strokes using the Benjamin, but I would be covered in sweat just trying to bring the pump up to pressure to open the check valve to begin to start to fill. I've yet to break a sweat with the Hill pump it's just a more efficient pump.
I have yet to use that rebuild kit for the Benjamin pump, and a week after buying my Hill pump I got deal on a tank that was too good not to grab, so now my Hill is for back up.
If you can fit it into your budget get the Hill.
 
I have used a Hill pump to successfully charge my Air Arms rifles for year. Recently, I purchased an Omega Supercharger and now primarily work off of a scuba tank, occasionally topped off with the Supercharger. But until you want to invest $2,500 plus in a tank and a quality compressor, the Hill pump will give you years of service plus a little extra exercise.