Asked and answered a million times. If you knew in advance what you might likely know after buying on eBay and having a problem, would most end-users buy again from eBay? Maybe that is the question and the answer can only be answered by those who have had problems.
Of course, the answers here may not be truly representative. Forums like this tend to only get a certain type of buyer who might take the time to respond.
If you don't mind not getting a warranty and then if it breaks and you suddenly find that UEI(Nevo) will not talk to you and will only talk to your dealer than I guess you would not buy again on eBay.
If it breaks you are basically out of luck. No warranty, no dealer to carry your flag forward to get a replacement, etc. No dealer to ask questions of, etc.
I replace Nevo's during the warranty for free with new product. That is what you get when you buy from a dealer who cares and knows the system. An eBay seller doesn't likely care and will not do anything for you.
Not every manufacturer is willing to work with the end user. Nevo is one of them who does not want to talk to the end-user. You must have a dealer do the leg work for you.
So, if you feel lucky, take the chance. If you prefer to have a more professional relationship and know you are covered, find a good Nevo dealer and pay the extra to do business with them. It is worth it in the longer run.