I couple months ago I created a launch page for my SAAS product using an Aweber form to collect emails during beta testing because I like their features. This worked fine before my application was actually complete and it served the purpose of allowing me to collect emails.
Now that my app is created, what can I do to convert those on the email list into users in my application or should I send out an email asking those people to create user accounts?
Should I scrap Aweber and just send out my own newsletters programatically. I would love to hear how others have handled this issue.
You should not create the user accounts automatically. First, you mention your launch page is "a couple months" old. It's common sense in the email marketing world that users forget about signing up in 4 to 6 months (sorry, but I can't find a reference for that right now). If that's the case, you should be sending a "Hey, we've launched!" newsletter with a clear call-to-action to sign-up:
That way, you will not only begin with a clear (albeit smaller) list of users with all sign-ups coming from engaged and active users, you'll also give your customers the power to create their account themselves. To make this as comfortable as possible for them, try to do a 1-click sign-up directly from the email.
For the email list management (sign-ups, auto unsubscribe, etc), I think any email marketing tool will do. I've used the both with success and no problems in the past:
Edit: I totally forgot about it, but it's worth referencing as a great tool for simple "coming soon" pages - LaunchRock.
I recommend kickofflabs.com. I just used their site. It is easy and their support appears to be top notch.