What are the weak points of Pass amps and pre-amps ?

I own the XP-20, best preamp I’ve owned.  I don’t have an extensive list of A/B’s to other preamps, so I wouldn’t be able to comment on what it lacks.  It sounds better than the handful of McIntosh preamps I’ve owned and PS Audio BHK pre that I demoed for a bit.  

It’s a very revealing pre.  You hear a lot of detail at low volume or high.  In my system, everything sounds authentic with it.  I’ve pulled it out and ran others, but with the XP, it just sounds organic, balanced in the high/mid/low regions and, well, as I already said, authentic. 

Had Pass 350.8 wonderful stage,bass,depth,imaging and powerful full bass didn't see any weak points.

Price. Value.

I have repeatedly been told they are very refined amps. Never heard a pair that made me wamt to take out a mortgage for them.

I have the XP12 and 250.8.

Really like them, the weakness is that because like most of us I like to try new things... but these are the first combo that I've been afraid to sell off and try something else!

So, suppose tempering the fun of research and upgraditis could be a weakness.

I feel the XP12 is really neutral.  I don't think the 250.8 is dead neutral, but it just sounds good with every speaker I've tried with it.