Are Mcintosh Tube Amps really all that?

I think it is taste. You can ask the same of any brand. Each listener has his/her own set of priorities that they desire in a product. Much as car buyer that buys for economy may not agree with on the buys for appearance. I think the McIntosh buyer is drawn to the product for a number of reasons. One can be appearance which can be novelty or cult(although they don't sacrifice live chickens anymore), another sound, another build quality, and yet another investment as they tend to hold a larger percentage of their sale price.
So I guess the same can be said of Audio Research, Conrad-Johnson or Krell to name a few.

McIntosh long ago mastered the black art of transformer design and winding. They build everything to one very high standard. Some of their designs, e.g., the MC275 tube amp, are still competitive 50 years later. I'm sure there are some here who had all Mac gear and then moved onto something else--Krell, ARC, C-J, etc., but (although I don't own any) I've found McIntosh in general to fully flesh out the music and provide dynamics and tonal balance that are easy to live with over the long haul.

In the early days of tube stereo products, McIntosh was 'it' in terms of reliability, low distortion specs., the Mac clinics, as well as visually with their characteristic glass face plates. They were second to none until Marantz showed up and gave Mac a run for their money. McIntosh has a following just like any high end audio manufacturer. Their products, generally speaking, are built to last a lifetime. Just like other manufacturers they have hits and misses. In their day they were considered the Cadillac of audio gear and many still feel that way.