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

Never owned the  X or XA series amps or preamps, but have always felt the earlier Aleph series were somewhat overrated, having owned the Aleph 2/5 amps, P preamp, and Ono/X-Ono phonostages.  The Ono/X-Ono, in particular, were so mediocre sounding compared to, say, a Jeff Rowland Cadence

We all hear differently. The Pass Preamplifiers and phonos are very neutral and what ever you have upstream, you will hear be it good or not so good. the thing is I do not want my Preamplifiers to sound like anything. Lots do unfortunately.  The Jeff Rowland stuff is good but I certainly would not say it blows away the older Pass stuff.  Synergy is the key in this hobby.  The Pass, ,older or newer in the right system can sound fantastic.

I have a Pass X250.8 and it is wonderful in my system . 
I don't know where all this junk about heating a room comes from(I only wish). Yes they do run warm and you can feel some heat within a foot or so of the amp. Another great thing is the high bias class A, mine hardly ever leaves this mode.

I spent a weekend auditioning the X260.5 monoblocks and the glowing weak point in my set-up is their lack of speed and attack. Just sounded lazy when compared to Bryston cubed series monoblocks and Simaudio monoblocks. They were musical no doubt but sluggish.  

In my observation, those whose hearing is good enough - no need for golden ear - hear very similarly but they can verbalize it in a different and sometimes unclear ways and of course, sound preferences differ. Most of people around me prefer electrostatic speakers, as an example, and I don't. 
As for the Pass gear, it doesn't appear to be for me, regardless of certain fine qualities that it has. I wouldn't consider Bryston or Sim Audio either. I would skip all that and go straight to Gryphon or some Swiss gear for transistor sound. No idea about Italian or German electronics.