I think it could depend upon your long-term plan for these pages. If it's all original, useful content as you say, then I can't see any negative effects of launching it all at once. The problem could come more in how you plan on promoting these pages and how many of these pages are going to be important pages within your website. If there are key pages, depending upon the team and resources that you have to promote these pages, you might consider releasing them over time so you don't have a glut of content sitting there without promotion in social media/PR/link building efforts because you don't have enough people-power, time, or money to get the word out about it all.
On the other hand, if your plan is just passive, receiving long-tail search traffic as the search engines work their way through all of that content, then why delay?