Has anybody had any reliability issues with VAC amplifiers?

When you say VAC amplifiers, I'm going to assume you mean vacuum tube amps.

In that case no. Fostex was the brand. Reading/always following the owners manual helps. 

I have a VAC phi 170 IQ power amp.  I haven't put that many hours on it but have had no problems with it, not even a hiccup.

Moe, I've never owned VAC gear, but have read a number of positive comments from owners here and elsewhere over many years about reliability and great support from Kevin at VAC...to a level above & beyond many competitors. So I'd suggest searching some more threads if you don't get much response here.
I admit I was a bit surprised by your post. Cheers,
Spencer

Yeah, I find your post's slant on VAC pretty surprising.  I've followed the audio hobby for decades and haven't encountered that sentiment before.  I have owned two VAC preamps and an amp and had no problems at all over the ~10 years of use.  I'm sure any manufacturer's line can have the odd issue or two, but I certainly haven't gotten the sense that VAC has issues in that regard.

I owned a Phi 300.1a for six years or so without issue. VAC's Sentry Circuit was triggered a few times, shutting the amp down when a tube went bad, preventing possible damage and worse. I would not own this amp without that safety feature. I believe all the IQ amps have it, so no worries.
I still have the matching Phi Beta preamp, which chugs along like a champ without any problems.

Long time VAC family member here.  A few issues directly tied to tube failures that were quickly addressed at the factory with excellent communication and fast turnaround.  Those were in my older power amps that did not include the Sentry Circuit.  My only other need for factory service was for some excellent upgrades.