It really depend whether you have a list yourself or it is a brand new product? If you already have a loyal list, then it shouldn't be a problem launching it.
You can definitely use holidays to springboard into an event. The whole "independence" focus for U.S. folks works well. You might want to try sending a proclamation for them to sign on July 4th so they are the first to get notified on July 9th.
Also, even though a "major" launch might not work well on a holiday, if you have a tight knit group you can do well. You'd be surprised how many people will sneak to their laptop to place a quick order they have already made up their mind to make.
Though a different time - I've a few successful launches on January 1. The start of the new year seems to focus folks.