We released a small update today that was causing problems for some people, so we pulled it before many people downloaded it. A new update has been submitted.
Alas, Simplenote for iOS won’t be available for download in the meantime, but hopefully not for long.
If you were among the small number of people who downloaded the update before it was pulled, and you’re experiencing a crash, please get in touch with us at support@simplenoteapp.com. Only premium users and those who have been using Simplenote since iOS version 3.x could be affected, and only if they happened to download the update during the hour or so that it was available.
Simplenote 
I uninstalled, bnoth on iPad2 and iPhone4, and then reinstalled while it was still up, and it seems to be working fine…