Nuvista Tubes - General


May I have opinions please on the pluses and minuses of Nuvista tubes versus vacuum tubes? Supposedly and from the basic homework I've done, Nuvista tubes purportedly offer high reliability, low microphony, low noise, consistency, and small size compared to their vacuum counterparts. So what's the down side? 
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Interesting bit of info as well that MF went to the trivistor when the Nuvistors dried up.
Musical Fidelity time-line http://www.musicalfidelity.com/about-us/timeline confirms that nuvista 1997 and trivista 2002, but why then (seeking speculation) would their current amplifier offerings utilize nuvistor tubes instead of trivistor? 
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I have owned the MF Nu- Vista 3D CD player for about 16 years. It is really a wonderful piece of gear. The sound is very "natural," almost analog in nature and is not at all "syrupy."  Pretty good for a metal encased micro-tube.

As for the Nu-Vista vs Tri- Vista issue, my understanding is that there were a lot of problems with overheating in the Tri- Vista components. I have read a number of posts on various audio forums attesting to that. The Nu-Vistas were designed to stay cooler than the average tube, so that may explain MF's return to its use.
and is not at all "syrupy." Pretty good for a metal encased micro-tube.
That's because it's got a transistor buffer after the Nuvista to drive the outside world with, without it it'd be "syrupy" if the Nuvista had to do the job.

Cheers George   
George ... then what's the point of a hybrid design if the transistor buffer controls sound quality?