Is there actually a difference?

I can tell the difference between ss and tube immediately. I feel the best ss amps try to replicate the tube sound with more bass slam. The class A ss amps do this very well. Love class A ss and tube amps. 

The only high power SS amps I have owned was a Krell and a Pass Labs. Heck at one time I A/B'd a Pass Labs X350.5 against the Pass Labs X350.8 and in all instances it was quite easy to notice the differences.

In tube amps I had a Atma-sphere M-60 3.3 and now I own the new Carver Raven 350. They sound more similar to each other than the solid states did.

ozzy

"...is it really worth the thousands you are shelling out to get that nearly-imperceivable .01% increase in performance?"

Only a person paying for it can answer that question. Some people drive Toyota Corolla, others prefer Lamborghini. Some of those with Lamborghini are fine with a Bluetooth speaker, while some with Toyota have more expensive audio equipment. It depends what you value at the moment of purchase and how much.

@erik_squires 
I've read almost all his articles and owners manuals and seen all his BA lectures. Can't recall anything of the sort. He doesn't worry much about the distortion of a pleasant sounding amplifier, but he doesn't design to add distortion on top of what the topology naturally produces with the exception of one of the FWs where he installed a knob to switch between positive and negative phase 2nd order distortion. Folks do the same thing with P3 on the complimentary BAGS and F5 too. All of the PL products are very low distortion though. 

Maybe it is just in my setup but I am certain I can hear a difference in solid state amps. Auditioned several amplifiers with my Tannoy XT8 speakers along the way.

Started with a Creek 50A - warm and very pleasant but not much energy. Moved to a Naim XS and definitely got a more solid presentation top to bottom. Then the eye wanders and I try the big Peachtree class D and the PS Audio 700 Monoblocks. Neither myself nor my wife could really every enjoy either class D. Dry and thin were the words we came up with independently. Strong dynamics but no joy. Could be the Tannoy sensitivity just not playing ball as plenty of reviewers like them enough.

Now I run a Hegel 160 though the week and a Primaluna Dialogue Premium Integrated on the weekend and any days I can just sit and listen. The Hegel has a great sound for a SS but the Primaluna is just so very nice. Might try me Sugden, Class A Luxman or First Watt next for a little bit of that SS warmth folks talk about.