Directory Submission and Press Releases are very very important. This is how you can get inbound links which really give a great contribution towards your page rank. Inbound links are directly proportional to the page rank.

Press release submuissions are definately very important. I have found press release submission to be an excellent source to boost traffic to a website. However I have also found that press releases are short term i.e the effect disappearas if you do not follow it up again in a couple of months.