I remember that one of the issues was that the menu was so large, you had to roll your mouse across the whole page to roll off of it and once again see the regular page content. Some people find this a pain; for others, it's a non-issue.
Another thing you might want to consider is SEO. This isn't personally my area of expertise so you could research further, but if your keywords are all within the content of your page, then the search engine has to read through all of your links before it gets to that content since the search engine reads top to bottom. On the other hand, if you purposefully want the search engine to hit those links first, then the menu might be a good idea.
