I've had my CMS50E for about a month now. Setting it up was pretty easy, using it is easy (spot checks, recording, uploading...). My concern is the accuracy, I cross checked the unit with an Octive Tech 300D and an Onyx II (Nonin) and found that while the latter two always agreed (say 98, 99) the CMS50E would sometimes be way off (91,92). Though sometimes it would agree with the other two the discrepancy rate is pretty high (most of the time it did not agree and was way out of the stated accuracy range). I tried swapping fingers, sitting perfectly still, everything I could think of and nothing seemed to help.
While I love the functionality of the CMS50E I am concerned about accuracy. (I'll try and take this up with the vendor or Contec directly, hopefully I have a dud that can be repaired/replaced)
Just posted this to give my impression, hopefully others are having better luck.