We have about a dozen Shurflo SRS backpacks. When they fail, it's usually a bad battery or a bad pump. Sometimes the fuse, but that's easy. Every spring, we take our non-working SRS units to http//www: sprayers.com They repair the ones that are easilly fixed, but sometimes they say we're better off just buying a new one. Sprayer Specialtes charges about $190 for a new one, but I have found them as low as $169 on ebay -- free shipping & no tax.
Bottom line -- I would not consider any other backpack sprayer, cuz the SRS has served us well....even with the drawbacks they have.
Proud subscriber of TURF Magazine. (thanks Ron)