Ive also so settled on Viperal Tasks as the least bad. I think the problem is all apps are slow opening on Windows Phone. Im so hoping this is fixed in WP8.
I just installed version 3.54 on a Nokia Lumia 920 (WP8) and when I launch the app it will not go past the splash screen. I sent an email to the developer but my past experience is that he is not responsive at all to emails.
Until now I used the app on an HTC Titan. With the latest version the repeating tasks feature broke. If I create a repeating task on the device, when I go back to edit that task the repeating settings are gone. The same happens if I create the task here and then sync my device.