I own and use the Johnny Stewart PM4 'Prey Master' - I am very satisfied with it's performance.
Battery life - 8/10
Durability - 10/10
Sound - 8 to.9/10
Wireless range - 9/10 (for line of sight / relatively flat terrain)
PROS: I like the interchangeable sound cards, which in my experience, like the entire apparatus are very robust and durable. I have used the device in super hot high desert, moist riparian and -8 snow conditions. It sounds fairly good and I like the jack rabbit calling sequence that came stock with the device. The wounded coyote pup is pretty good too, both alone or used alternating have called predators to their death. You can order a separate 'coyote bark, howl, etc' card or a rabbit variations card... if e-callers are legal for snow geese in your area, it has a pretty good snow goose sound card too. There are numerous soundcards available, which I have found online and in stores ranging from $19.00-$30.00, bass pro shops had turkey call cards for $12.00 clearance even (e-callers are illegal for turkey & most other game animals here in California, predators are legal)
CONS - the factory pre-loaded sound cards have some cheesy sequences & you can only use Johnny Stewart brand sound cards. The buttons on the remote can sometimes act up (hard to press to start / stop) perhaps it is a design issue, although it generally occured when it was extremely cold. The wireless functions well; except when battery life is low - then the remote is hard pressed to communicate with the speaker unit. The speaker is green, yet it could be a bit less glossy.
Overall I give this product an 8-9/10; not just because I own one. I fully intended to get a Foxpro, for the venerable and proven durability, wireless capabilities + MP3 features... but I never could save 300+ for a caller. So 2 years ago I was given this as a gift, which came as a surprise - 2 days later, this call was 50 yards in front of me - with a dead coyote 20 yards away from it.
If I had to do it all over, I would get a Foxpro - which also have the dangling / moving / integrated fuzzy tail decoy thing... but I will probably never do so. For 150-200 (half the price) I already have a durable, proven e-caller.
So if you're a bells & whistles guy Foxpro is great; but the J.S. + $15.00 rabbit decoy has proven to be damn effective for me as well.
Why? One inquires why? Because, AMERICA !!