loading time depends on all the parts but HDD is the biggest bottleneck if you have a relatively new computer. Rams are no longer the bottlenecks since most of us already have at least 4gigs of DDR2s. It is our aging mechanical HDD that really cripple the speed of our computers.
i see , well i wouldnt consider my hdd old , but its the first time in gaming i see
the new star craft 2 taking some time loading some maps , comparing to
other games , where my pc still loads them at good speed .
i think with online games, and i haven't played SC2 so I can't say exactly but in multiplayer games, you sometimes have to wait for the other people to finish loading before YOUR game finishes loading, if that makes sense. I've noticed it on some games where my machine loads a map/whatever at 100% but will sit there for sometime until the other people have loaded and you all join together. Maybe thats not how SC2 works, but hope it may help.