WinRAR works well.
I just completed DSM 01.j2l (what I assume is the first level) and...wow. The eyecandy is great, and there are lots of little secrets. My only complaints are there are too many fastfires and some of the floating platforms look out of place. I'm partway through DSM 02.j2l. I love the lava wall effect and layer 8. Unfortunately, some platforms in the BG layers look like they belong on layer 4, and are confusing. I'll edit this post when I finish the levels. Oh, and I assume the second level isn't finished, as it cuts off suddenly. Now to test the third level in the RAR file...
EDIT: Okay, upon playing, I learned "!Wanderlust.j2l" was just a readme level. I did like the readme tileset though. Excellent first level and tileset. I look forward to seeing this pack progress...