Of the DM4 maps I have played, I have found them much more approachable than the crushing difficulty of Arcane Dimensions.
Of the levels included, some of my favorites are the "Deimos Revisited" By Shades which is a complete rebuilding of E2M1 from the original Doom, and "Badly Placated" by ww. Although to be fair, this map pack is huge and I haven't played it all yet.
Download the expansion here.
Some gameplay videos are listed after the page break.
Deimos Revisited played on Nightmare difficulty:
The Bad House Played on Nightmare Difficulty:
A Pact Beheld played on Nightmare Difficulty:
Special thanks to Kills Alone for uploading these fine gameplay videos.
Check out his awesome channel.