Callbacks were created by the v0.1 with just empty function handling them which was doing nothing after the callback - with the intent to implement it in v0.2 and be fully compatible. I am however reviewing the v0.1 code and it seems that the callback URL was missing one of the parameters that are now required and callbacks created by the v0.1 might not be compatible with v0.2, sorry for that. The only effect might be that donations won't be detected and displayed correctly, but they still go to your destination address. I'll release next version around the weekend and will probably include feature to re-create all existing per-post addresses (e.g. to change destination address to forward coins to) so there's no need to manually deleting the current addresses (you can do that and new addresses will be created immediately, but then tips to old addresses will never be included in the stats; re-creating addresses using the feature will preserve previous addresses as well so their tips will be included in the stats).