I think I did that level in more or less 10 tries, same with the stone guy comet with 1 life...
I REALLY take some time to pass the purple coins at the dreadnought, that was insane... 50 lifes at least...

That level isn't very hard if you do it correctly. I remember the first time I did it with Mario, I probably did the level at least 20 times. My second play through with Luigi (6 months later) I did it in 1 try. So I don't think it is that hard, and maybe you're confused because there are actually way more than 100 purple coins in that level (so you don't need to get everyone of them).

Oh yeah some tips, go around the level in a clockwise fashion, and long jump from the starting platform as far as possible (you need those close green squares when you come back for the star).

The only coins that are extremely important to get are the 4 long jump ones on the right side of your starting point. These are long strings of purple coins that require a nearly perfect long jump to get all of the them, and trust me if you miss those you might as well start over again. I found that you couldn't get them properly without going around the level going clockwise.

Also Scottie's map on the first page is good i think, pretty much what i do and although it took me a few tries with Mario i also got it first go with Luigi.

BTW, some people thought the Manta racing was hard...........?

Eh, I never actually beat SMG, maybe I should.......

YOU REALIZE YOU DON'T NEED TO GET ALL THE PURPLE COINS, JUST ENOUGH TO MEET THE QUOTA!

I wouldn't call it hard, but I found it really damn annoying. The control set-up is really weird and unnatural. (Why not handlebar style?) Combine that with all the rapids, and you're constantly bouncing around anytime you attempt anything greater then a snail's pace. I had to redo it a bunch because I'd get impatient, fuck up, and die. =P

I'm pretty sure the second stingray race gave me a harder time than this level did.

Still, it's a good challenge. Something about the hard levels in this game kicks my ass without makng me so frustrated that I want to quit.

Thanks everybody! I just did it now. All I did differently than before was to spin after some of my jumps and be sure to properly position the camera. I beat the rest of the purple coin challenges as well. Now it's time for Super Luigi Galaxy.

Yep, that level caused me the most grief. Man was it hard.