This would be my concern as well... in the description it says all passwords are stored securely in the local keychain. Seems safe... I would be concerned if I were one of the folks who buy pirated cydia tweaks though.
My main use for this would be my bank account and credit card apps so I would be a little hesitant but I think I may take the plunge, just not as an early adopter.
Well that's mostly why I'm waiting. I don't tend to trust third party apps when they first come out. Not saying I'm suspecting this one of being malicious at all, but I have simply way too much to lose in the way of passwords and such and I'd rather make sure I don't.