I was given a new in the box MSR Sweetwater purification system. Have you used one of these and how well did it work? Thank you!

It's been discontinued. It's the filter I've used for the last several years. It works well, but it does require brushing out fairly frequently to keep good flow. It's a pretty tough filter, and can handle more abuse than others of that era, but I think it's been discontinued for good reason: the new filters are smaller, faster, and more reliable. Still, I intend to use mine until it dies, it's good.

+1

I have one of these but I don’t use it much anymore. It worked good for many trips to the BWCA. You need to brush it out a few times during the trip to get the flow back. I now use a gravity type filter.

I bought one in 2005 (?), and it has seen EXTENSIVE use in the Eastern woods on backpacking trips. It still functions pretty much as new, and is on the second filter. The filter is like, some kind of porous stone that can erode while cleaning it with the brush. Nonetheless, it's a proven piece of kit.
Reliable, easy-to-clean, and packable. Never let me down in dozens of trips.
It clogs more frequently than I'd like it to, so I bought a Platypus 4L gravity system a couple years ago. I prefer the gravity system immensely for canoe tripping -so convenient, and mass quantities of H2O.
But I'm still hanging onto the Sweetwater because I'm a hoarder, and it works.

EDIT: I have never used the bleach drops that MSR overcharges for in the kit... Have I been using it incorrectly this whole time? Never gotten sick from waterborne illness when using the filter. -Got camphylobacter jejunate once when I accidentally swallowed LOTS of Delaware River water in NY's farm country. That was no fun, but very easily resolved. :)

I think the troop has 2 on the shelf... Had to use the silt stopper or else it would plug up. Switched to Aqua Mura one year and brought the Sweetwater as a backup. Since then I don't bring it. Gotta pump a lot of water for 8 people. Too much work...

dr bob