After 1 1/2 years I have tried almost every brand of salt. I can attest to Oceanic's high calcium content--the times I've used it I get between 550-650 ppm. The Alk is also usually a bit low w/ oceanic--I get about 7 dKH.
Coralife salt gave me pretty good results with calcium and alk, but there were alot of fluctuations w/ salinity. Seems like every batch I mixed w/ it had different salinity readings with the same amount of salt added. (BTW, I measure with a refractometer.)
Instant ocean gave me good results starting out, but I wasn't yet knowledgable enough to know the difference. I have since stopped using it because of the "killer alk" batches I have heard about. (Ask Thomas712 about this or do a search on this forum to read more.)
I now use Tropic Marin Pro Reef and I'm completly happy with the results. A constant salinity, Alk at 11 dKH, and Calcium at 440 ppm every time. Also, to my knowledge this is the only salt mix with no documented problems or bad batches.