Ok, Nick, here's my feedback....
First, it really doesn't sound all that bad. not TOTALLY pro, but not bad at all for a hobbyist.
However, i think the thing that's going to help you the most here is to open up the stereo spectrum. You've currently got your "rain" sounds spread out pretty well, but the drums are pretty close to the center throughout, as are the strings.
I personally hate the sound of a "lopsided" mix, but if you put everything close to dead center, it'll sound cluttered. You really want to leave the center channel open for the lead track... What are you doing for drums? a drum synth program? Try to picture the way a set is laid out in your head (or, if you can't, look at a picture of someone else's kit), and try to pan everything you're going to be using as it would be laid out in the kit. I generally do something like kick just to one side, snare slightly to the other (we're talking 5% off center, perhaps), high hat a bit further out, and then ride cymbols at least panned out 50%, probably more. Tweak it until it sounds right through your speakers.
Also, your drums sound a little over compressed to me- listen to the high-hats. their "reverb" changes in character a lot depending on what else is being played on the "kit" at the time... I'd compress them less, and you might also want to try reverbing them post-compression.
The acoustic guitar is trickier here... there's a few things you could do to preserve that sense of symetry without cluttering the center chanell. You could either double track it and do one left and one right, you could simply copy it and either do a slight delay on it or leave it unaltered (or maybe a heavier reverb on one, a chorus, etc.), or you could push the acoustic out about 25% and put the synth on the other side. your call.
The acoustic is also too bass-heavy, IMO. I LOVE the sound of a nice, full, rich acoustic guitar... but in a thick mix like this, some of that low end has to go, IMO.
I'd also take the "rain" sounds way down once the music kicks in, possibly cutting them altogether.
As for the lead guitar itself... I think opening up the mix more would help it a lot there, on it's own... But (since I'm guessing you're going for a "Boston Rain Melody" sort of vibe), compare your tone to Vai's on that track. His tone has a bit more prescense and high end cut to it, and a slightly more attuned bass. It also, as LGMT pointed out, is slightly less compressed, although a lot of that might be that it's simply slightly cleaner than yours is. And if you'll notice, it's got more of an upper mid focus to it than yours does- it really helps it cut.
Also, i don't think the drums and acoustic tracks are tracking perfectly- some of the rhythms seem a little off in places. Were these live drums? If so, maybe try tracking agaisnt a click track. A tighter feel will always make something sound more "pro," all other factors being the same.
Idunno, hope some of this is useful... Your lead work is great, BTW.