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

How about this approach? Purely cumulative - no back-tracking, and only iterates once. For raw performance, I'm not sure you'll do better with LINQ etc, regardless of how "pretty" a LINQ answer might be.

using System;
using System.Collections.Generic;
using System.Text;

static class Program
{
    public static string CommaQuibbling(IEnumerable items)
    {
        StringBuilder sb = new StringBuilder('{');
        using (var iter = items.GetEnumerator())
        {
            if (iter.MoveNext())
            { // first item can be appended directly
                sb.Append(iter.Current);
                if (iter.MoveNext())
                { // more than one; only add each
                  // term when we know there is another
                    string lastItem = iter.Current;
                    while (iter.MoveNext())
                    { // middle term; use ", "
                        sb.Append(", ").Append(lastItem);
                        lastItem = iter.Current;
                    }
                    // add the final term; since we are on at least the
                    // second term, always use " and "
                    sb.Append(" and ").Append(lastItem);
                }
            }
        }
        return sb.Append('}').ToString();
    }
    static void Main()
    {
        Console.WriteLine(CommaQuibbling(new string[] { }));
        Console.WriteLine(CommaQuibbling(new string[] { "ABC" }));
        Console.WriteLine(CommaQuibbling(new string[] { "ABC", "DEF" }));
        Console.WriteLine(CommaQuibbling(new string[] {
             "ABC", "DEF", "G", "H" }));
    }
}