I own a Keeler and a Heine BIO. But I'm actually trying to sell the Keeler though. The working distance in the Keeler is too long for my shorter arms, so I tested the Heine and it was more suited for me (4' 11", short arms).
Besides my personal issue, the Keeler is pretty good. A few SCCO students purchased the Keeler LED wireless in my class. It is true that the LED casts a different color to the fundus image - some of our staffing doctors don't like it, while others don't mind it.
In regards to patients, just like any other BIO, don't blast the illumination too high and they'll be just fine.
The advantage is definitely the LED lights low power consumption. I hardly ever have to charge my BIO! And I really really like that it's wireless.
If you're still interested and want to purchase a used Keeler Vantage wireless LED BIO, contact me. My BIO is in perfect working condition and still under warranty through my school. Asking for roughly $2,200 for everything that came with the package including BIO, chargers, batteries, accessories and case.