I bought this model exactly 3 years ago. I have used and continue to use it for farm animal, equine (repro only) and small animal purposes, and it has not malfunctioned once. The batteries do last well after a complete charge, and the device is relatively easy to use. Picture quality/resolution is very good, for the price, IMO. I have only used the linear (rectal) probe, including improvising its use for small animal work, with generally good results. The small animal side of our mixed practice is not busy enough to warrant me buying the convex probe, but I will do, should things get much busier.
I had to make a bespoke wooden protective box and waterproof cover, to protect the device during farm/equine use, which took considerable effort. The device certainly isn't waterproof, but with minding, will last and serve well.