I have a HHKB and a mouse setup with Satechi desk mat.
I've thought about getting an extended mouse pad, but decided to roll the dice with this.
Overall, the size is perfect in my opinion, and fit and finish is nice.
It is very thin yet has just enough cushion so the keyboard sounds don't resonate with the table.
The only downside if I really want to nitpick is the roughness on the contact area of wrist. If I really concentrate on that feeling, it is admittedly not good, but in day to day life, I don't notice it.
I will post some pics when I get home, just wanted to share a short/quick review.
Btw, it looks 10X better than a mouse pad!!