The first one was a little tricky since you needed some pretty perfect timing (that is, if the Thwomp crashed down a second time, it would be too late). The third one was very clever, I thought. I actually took a picture of the bouncing Koopa in hopes of saying that it was placed stupidly, but upon going to the left, it was actually the total opposite. Getting into that little area is kind of tough, and you should probably consider making the spiky opening a bit bigger .. but other than that, it's pretty cool.
By the way, in regards to the length: have you considered chopping out that last little bit after the third SMWC coin, and actually making the last part the Roviclaw area (with a bit of an extension, I suppose)? Sure, you'd have to move that third SMWC coin, but if you make a giant Roviclaw section, it should be really easy to find a spot to hide it. I can still think of a couple of gimmicks that could be mixed in with it so that it doesn't feel too repetitive:
-Timing a P-Switch press so that you can pass through some used blocks (now coins) with the Roviclaw.
-Falling on a springboard, and using it to spring to a higher Roviclaw.
Those two ideas, at the very least, might help in drawing your level to a close.
(I think a little piece of me just wants to see more usage of the claw at the very end, so eh.)
By the way, in regards to the length: have you considered chopping out that last little bit after the third SMWC coin, and actually making the last part the Roviclaw area (with a bit of an extension, I suppose)? Sure, you'd have to move that third SMWC coin, but if you make a giant Roviclaw section, it should be really easy to find a spot to hide it. I can still think of a couple of gimmicks that could be mixed in with it so that it doesn't feel too repetitive:
-Timing a P-Switch press so that you can pass through some used blocks (now coins) with the Roviclaw.
-Falling on a springboard, and using it to spring to a higher Roviclaw.
Those two ideas, at the very least, might help in drawing your level to a close.
(I think a little piece of me just wants to see more usage of the claw at the very end, so eh.)