Assuming you actually get listed in DMOZ, and that is a big if, you may see an improvement in rankings but most likely not. Although a link from DMOZ is more valuable then a link from a regular directory their links aren't as powerful as many people like to make them out to be. Unless the search terms you hope to rank well for are very niche specific I wouldn't expect that link to make any kind of difference. But it is good to have.