There is a bug in the 1.1 release that makes it very, very hard to keep the health of your pet up. I didn't catch this bug until after 1.1 was released to Apple (and then I had to wait for it to approved for sale before I could update the binary again).
Anyway, this is now fixed in the 1.1.1 release. I've sent this off to Apple, and it should appear in the App Store in the next couple of weeks hopefully.
Additionally, there are a few other changes:
1) Reactivation codes are gone in this version. If you are a really bad parent, you won't need a code to reactivate. Be careful though, you can still lose your pet if you neglect it too many times (in which case, the program will simply restart).
2) In version 1.1 it was possible to go into Gotcha debt, especially if you neglected your pet. In version 1.1.1 the lowest amount of Gotchas you can have are 0
3) One new item has been added to the store in the Food section. It's a German dish called Sauerbraten!
4) You can now set the type of giggle you want, either the original or the new version
5) You can now set the maintenance level of your pet. Low, Medium or High. A low maintenance pet uses less resources over time.