I tried again for the black pearl achievements and failed... I just don't have the patients for it. I can get 3 or 4 stars by the end of the first level, then I can build the 4x4 grid half way through the 2nd level, but I'm horrible at managing the gird, it's constantly collapsing and I accidentally join star clusters together all the time. it's a mess.
If you want to see some ridiculous Hexic players check out youtube. there's one video of a guy getting the black pearl cluster by the end of level 1
Also check out the Hexic board in the Official Xbox forum, some ridiculous players there and lots of good strategy.