Lumines fans will enjoy it, and it makes a good companion to Lumines Live, but don't expect anything groundbreaking.
I had mixed reactions, but in the end, I am satisfied with my purchase.
At first when I popped in the disc, it became immediately apparent that I was playing it on a PS2. The PS2 has never done 2D graphics very well. The edges of the blocks and text tend to have what I can only describe as a "shimmer effect" which detracts from the quality of the visuals.
The sound is not nearly as perfect as it was in the original. Lumines II players will recognize the pause in the music (but not the gameplay) when switching between skins in Challenge mode.
Lumines Plus' content is essentially the opposite of Lumines Live; Plus consists of the original skins and music from Lumines, plus some additional skins pulled from Lumines II, while Live contains mostly Lumines II content with some recycled skins from the first title. The two games compliment eachother nicely.
All of Lumines Plus' problems can easily be dismissed, because when you come right down to it, Lumines is an awesome game. If you love Lumines, or have never played it before, you should pick it up. Plus offers all of the enjoyment of Lumines without the hand/arm/neck cramps of the PSP experience. It's nice to have the option to play the game on a console.
At it's core, the only real difference is that it's on a bigger screen with a more comfortable controller (and probably a better sound system). For a good deal of Lumines fans, that's enough to warrant a purchase. However, if you don't like the idea of buying the same game then perhaps you should pick up Every Extend Extra instead.