I have 2 C2s and 2 C3s. Very happy with their quality, as are many of the members here on CPF. Maybe your experience is based on some earlier models?
I have to say Ultrafire is the worst brand I have ever seen.
There are many producers in China who sell "Ultrafire" lights and batteries.
These "Ultrefire" products has the same mark as "Superfire".
I have 2 C2s and 2 C3s. Very happy with their quality, as are many of the members here on CPF. Maybe your experience is based on some earlier models?