Eric Lippert's challenge “comma-quibbling”, best answer?

Question

I wanted to bring this challenge to the attention of the stackoverflow community. The original problem and answers are here. BTW, if you did not follow it before, you should

Answer 1

Late entry:

public static string CommaQuibbling(IEnumerable items)
{
    string[] parts = items.ToArray();
    StringBuilder result = new StringBuilder('{');
    for (int i = 0; i < parts.Length; i++)
    {
        if (i > 0)
            result.Append(i == parts.Length - 1 ? " and " : ", ");
        result.Append(parts[i]);
    }
    return result.Append('}').ToString();
}