I took a week long trip to WDW last April, and rode SM for the first time, and rather enjoyed it. I waited a good 45 minutes, but that is to be expected. Also, something HAS to be done with the waiting line; I got dizzy and felt sick several times through the line. I wasn't even on the ride yet!
As far as the ride itself goes, as I said, I rather enjoyed it. A bit jerky, but you felt out of control. I liked it. I have never rode the DL version of SM, so I can't say which one is better.
I personally feel that they should gut the entire thing, and put all new materials in there, while retaining the EXACT same track layout. New track, new supports, the whole thing. But keep the same track design. Also, it needs to be PITCH black dark. Maybe with glowing stars in the ceiling, or something like that. New effects are a must.
Something that I think would be cool, would be if they biult neon onto the outside of the biulding, and had it lit up at night. THey could have a light show at night, and when it is not in use, they could make the neon shine white, and a very space age look to it.
Just my two cents.