[Edit] I bought this game on release back in mid February, since then there was one update, I didn't notice if it even did anything. Back in February people asked when more songs would be added, and they mentioned upcoming DLC packs, which have never come out. So if you're a cautious buyer assume the game has been abandoned for better prospects. It's currently on sale for $7.50, maybe not a bad price for an hour of entertainment for you. That said, none of my complaints have been touched and the game never really received any real update. End edit.
I will preface this by saying, I enjoy the game, I sing, and I'm well versed in the genre in my opinion.
Unfortunately this game is fairly questionable. The pitch detection tends to be all over the place as it's picked up my non-vocalised coughing as a part of a song. On top of that the intros, and subsequently exits, for a lot of the lyrics could be greatly improved, in a lot of songs it can be from .2 to .5 seconds ahead where the actual music is. There is a distinct lack of quality here in comparison to console karaoke games like SingStar.
-A handful of songs have non-sung parts that you still have to speak.
-The song menu has questionable UI, you have to click every song and you can't scroll or use arrow keys by default.
-Playing random songs in the pause menu is rather distracting and annoying, you tend to pause for a reason and putting a completely different song in someones head is not a good idea in a karoake game.
-The track list has a lot of good, but many terrible songs to sing, this is not a judgement of whether the song is good or bad but whether the song is good or bad to sing. If the track list were, lets say, 100 songs this would be less of a problem, but the track list length isn't one of my complaints.
Overall I'd give it a 5/10, completely enjoyable but definitely not good, with it's glaring flaws, minor annoyances, and the fact things like Karaokeparty already exist online for the pc and things like singstar exist on consoles. This is just a weak entry to the genre of karaoke games, and while it may be the 'PC's first' it's probably going to be end up being known as the PC's worst.