New Funk Firm Achromat Warped

FWIW, I received my replacement Achromat and it's perfectly flat.

Sounds great on my Technics G. As with the GR the Achromat enhances midrange clarity, focus and separation of instruments/voices compared to the stock rubber mat - sounds really pop. So my impressions are completely opposite to @avanti1960. Some may prefer the more laid back sound of the rubber mat.

I received my red APM Achromat from Funk Firm; it is flat. The differences are subtle, but it does improve clarity in the mids and highs. Bass notes are rendered with a bit more texture. One downside is that in order to get the VTA correct with a 180gm LP with my Quintet Black S the tonearm height just makes it when maxed out. I might be able to obtain a bit more flexibility with a headshell other than the Technics. It isn't an issue with the VM760SLC on A-T headshell.

I'll run the Achromat for a while before experimenting with a different mat.

The differences are subtle, but it does improve clarity in the mids and highs. Bass notes are rendered with a bit more texture. 

I don't find the difference (to the stock 3mm rubber mat) subtle at all.  I like  how the clarity extends to instruments at the back of the stage  - increased transparency if you like. There is also much better articulation of instrumental and vocal detail - easier to hear how an instrument is is played and changes with different technique. So lots of nice things happening and not at all in a 'highlighting' sense, it just seems to be doing a better job of allowing the recovery of recorded detail in an uncoloured manner. 

While I don't have a Technics table, I have tried the Achromats on a bunch of different tables.  All with excellent results.

One of my favorite mats...and I'm kind of a "mat"aholic, so I own a lot.