For people looking to use apps, please consider the likelihood and impact of one of these companies disappearing overnight. Some of them are tech startups without a sustainable critical mass and they could shut down at any time.
If your landing page provider stops providing service, it's probably easy to recover if you have copies of all the email address collected. If your planning and project management tool disappears with all your data, there could be a significant cost.
I'd bet that half the services on this page will not exist in a few years time. If the success of your business relies on them trading, pick carefully.