I have a wishy-washy opinion on the game. I like most of the setlist, I enjoy the unique look/tone that the Lego elements give it, and I think it has some neat innovations that could serve the series well as a whole (especially the album-recording element, that was great).
However, even though I did say I like most of the setlist, there are 4 or 5 real stinkers (which I'll refrain from naming). This is not really a knock on LRB, but the export - For $10, I really wish I could have chosen which ones would make the transition into the Rock Band 2 library. With RB1's export, I was able to say goodbye to a couple of songs I couldn't stand playing, and I really hope an RB2export will someday allow me to say goodbye to "Visions." This "All or nothing" approach with exports (I ran into the same problem with the AC/DC pack) is pretty infuriating.
That pretty much sums up my opinion to a tee. After I do the LRB export, I'll be scared as hell to do a mystery setlist in RB2. I give LRB a solid 7.