Futterman H3a OTL amp for sale seen on on eBay!

I can only tell you of my experience, so there is no spreading of rumors, myths being perpetuated or anecdotal accounts being said here. This Futterman has been driving KLH Model Nines since 1972. I don't know how that "reputation" came about, but in today's lingo i might even say its fake news.

Early ones had stability issues.
http://www.atma-sphere.com/Resources/OTLs_Defined.php
Reading more, it seems JF improved the circuit and fixed the issue. 

Futtermans like high impedance and were designed for 16 ohm and above speakers.  These were very popular in early hi-fi. Will work OK but the low limit is 8 ohms.  They are much more efficient the higher the impedance.  Never heard of them taking out output tubes.  A very novel tranformerless design.  

Also note many tried to drive low imp speakers with Futterman OTL which looked for high imp ( such as KLH Model Nine 16~30 ohm ) loads. When driving low imp designs when the impedance dipped to 4 ohms or less it would oscillate. ALL speakers have a varying impedance, it depends at what frequency is being delivered to the speaker when the measurement is being taken.