Initially, I was not that impressed with MEGAWATT.WAD. There is no entrance door, which I find detracts from the realism somewhat - especially when that means you start in a corridor that leads nowhere except onward, it is nice to think that a corridor leads somewhare, if only to the entrance. The early rooms are cavernous - too large and empty (well, not that empty) and bright, and the STARTAN wallpaper doesn't look that impressive. Also, the second room has door leading into a low corridor with no lintel - the door just tiles all the way up the wall. The author wisely used the DOORHI texture, which tiles OK vertically, but it still isn't perfect.
Having said that, this level improved greatly with time. A mixture of Knee-Depp style halls at the start, some darker stone areas, and some dark green marble rooms, this level has some variety and some interesting architecture - the rooms become more interesting as you progress. The textures are clean, with no glaring errors or texture mis-alignment. There are some very interesting features later on.
Some of the secrets are concealed by making their map lines invisible instead of red - so you can't see they are doors, but can see something odd is there. I am not sure I prefer this to the tried-and-tested method of making the texture slightly different, or puting some kind of marker in sight, but it works well enough. There is one place that you can get stuck (fall in the acid, can't get out), but mostly the author has catered for this well. There are also some places where you must make a "leap of faith" (jump into the slime and hope some stairs or a bridge appear soon), which could lead you to get stuck as described above if you try it too often.
As to the gameplay, it is good. It is no stroll in the park, with a baron to be defeated using shells early on, and a sprinkling of cacos. If you play carefully, I suspect you could do it in 1 or 2 attempts at UV. In the end, I finished with health to spare. There is too much ammo toward the end (though I chainsawed for a while), but since this leads into MEGALAB, this is OK.
MEGALAB.WAD continues to improve - it has some very impressive rooms, and the play is very interesting. I especially liked the half-open corridors near the start - it gave the level a distinct style. It is well interconnected, but large, so was a little slow to play in places. There was still plenty of ammo, but it was mainly shells, so fighting the packs of cacos was still a challenge. Personally, I'd redecorate some of the green marble areas - I don't think they fit the style - but overall a PWAD to be played.
My only complaint is that at the end, the level is very empty, so searching for the exit was dull (a few pointers, coupled with a few final surprises, would have improved this greatly).
A good PWAD to play, worth the download. PWAD designers should see the half-open corridors at the start of MEGALAB, they are a could example of giving a level a style of its own.