Thanks for the feedback! Keep it coming!

I'll run through the points each of you guys brought up in order so I don't miss any.
I will look into more upsale in the trial. It definitely should be clear on its own, without reading the website, what a customer is looking at and what is possible in the full version. I don't think a beta claim is necessary as I feel the game is pretty polished and quickly becoming even more so. Feedback can be left in the forums. I don't think having forums in-game is really feasible.
What you see on the site is the best I can do art-wise. I actually take it as a compliment you think it is nice as it is.

I don't think I can make it any nicer really, I wish I could. The site is designed well and could definitely look different, the challenge is how it would look. Ripping another site for design ideas is good, but I can't exactly take all their art. I can only rip ideas that I could reimplement myself, which is the real limiting factor.
Not sure I'd say the git-scm site looks really cool. Is that a brown tooth eating trees?

It does present information clearly though. I'll give some thought on how to make the homepage convey the information more clearly.
tackle, no worries. I figured you got sidetracked by real life.
The best way to sing with the original artist's vocals is to use a music file without vocals. SingSong supports a naming convention for this so you don't need a set of lyrics files for both the regular and the instrumental version...
http://singthegame.com/faq.php
The only other solution for this is what karaoke machines do: Analyze the stereo music and reduce in volume the frequencies in the human vocal range that are present in both the left and right channels. This works because generally the lead vocals are located in the center of the mix. It really isn't very good though, because it can ruin certain music like a guitar solo and doesn't work well at all if the vocals are panned off-center.
Considering the effort needed to implement my own voice removal, at this early point in the game's life I don't feel like this is enough of a must have feature to spend so much time on. Plus there is a workaround: I'm sure there are free programs out there that can modify a regular music file and produce a new file with the vocals toned down or even remove entirely (in the best case).
For those that are really into it I can see not wanting original voices. Personally though, I need the original voice there so I have some idea of what I need to do. Also it helps mask the player's voice, which helps a lot of people get over the embarrassment.
Right now I want to focus on making it available and building a community. After that I want to add multiplayer modes where you can play in teams, play king-of-the-hill, pass-the-mic, tournaments, and other fun multiplayer games like random effects such as sing without lyrics or without note bars or arrows. After all, karaoke is the most fun with a group of people!