Some of us, maybe most of us lives in a city environment, what means an electrical noise floor of S8 to S9 on HF bands. To hear weak QRP stations could be difficult. When I was on the island of Ameland a few years ago I noticed a low noise floor on HF, but now I realized I was using a magnetic loop as well. Maybe a combination of the two. So I consider a magnetic loop for HF to lower the static / electric noise. Most of the time I use ‘fixed’ frequencies for JT65, PSK31, JT9-1 and QRP CW frequencies. So constant tuning is not necessary. That could be the most annoying thing: constant tuning especially when you like to switch a lot from frequencies or band. Another thing: you can place a Magnetic Loop in the attic or bedroom, so pretty stealth for the neighbours. Or outside on a pole for those with little space in the backyard.
More info: http://en.wikipedia.org/wiki/Loop_antenna