I second the MSR G/K. Mine has given me perfect service for about as long as has Tom's. Hot, burns just about anything, easy to maintain, and reliable.
I have used a Trianga alcohol burner in a Swedish cook kit and it is slow slow slow compared to the MSR.
For water boiling only using natural found fuels I really like a Kelly Kettle....you may want to take a look at my article over at JM Outdoors.
http://outdoors-magazine.com/s_article.php?id_article=126