This is probably my favorite set of maps ever. It feels like playing original Quake in the 90's. The difficulty and gameplay is simple and clean and fast. Everything is easy and smooth, in a good way. You just blast through the maps, as if you were doing yet another run through of Quake. I think it's really hard to replicate the actual id1 Quake feeling, not to mention across several maps!
My only critique is that the last battle's difficulty is disproportionately more difficult than anything in the rest of the map pack. The criticism isn't the difficulty itself - that last map, as a stand-alone map, is super good on its own! It just doesn't fit the old-school pace of the rest of the map pack.
So it's not a complaint, just pointing out how it feels mismatched. It's all good fun, and I hope it inspires more map making that returns to the roots of simple (but thoughtful) texturing, fast-paced gameplay, easy old-school secrets, etc.
I look forward to the next map/s by Tonhao!