This is my first experience with Wario Land 4 and I tend to agree with other first-timers.
It's a fun game with novel ideas, but I think that's where it annoyed me. The expanded life bar only insulted me at first, suggesting that I'm in for a world of hurt and need the supposed "handicap." I grew up in older style 2d side-scrollers and if it something moved, I stay away from it. The game knows this but didn't tell me it's not the standard here. The idea of using status effects to solve puzzles is great! However, I have to find out by accident. This would generally be forgivable, BUT the game tosses in enemies that do nothing but damage you, reinforcing the original teachings to avoid all moving things. That's where the game gets frustrating. I don't like being expected to fail to succeed. If I fell down a pit, it's because I messed up... surprise! I was supposed to drop there to find a treasure. Now I find myself chucking Wario down every hole.
If you look at DK94, there are little cut scenes that show the general expectations. Without that, the game becomes a child with a fork kind of mentality: Let's see what responds to pokes!
The level design is great for a portable, keeping things tight and simple with a move forward until you can't anymore then move up/down. I agree with other sentiments towards the time trial back. Thankfully, the game encourages a enough exploration to identify where detours will occur, but the rush of making it back in time creates the central, most addictive, trait of the game: Greed. Do I go for the money or will I not have enough time to make it back? I think that's where the game shines. Naturally, we quickly develop a "Yeah, I can get that in time!" judgment process, but it creeps up and gets worse as the game goes on. To THAT, I say kudos.
So far, haven't felt compelled to race back through a level to scavenge for what I've missed. The short levels unfortunately reinforce this instead of discourage it.
Other than that, the art is wit of the game is great and it controls nicely. I just wish it assumed less.