While I don't believe that High Intensity Interval Training (HIIT) is the only worthy form of cardio, I do firmly believe it is the ideal form of cardio for those individuals who are looking to lose weight and lower body fat for reasons addressed in my Understanding EPOC article.
With that said, I'm also convinced that HIIT is often incorrectly performed as I hear over and over again from individuals that they perform HIIT for 45 - 60 minutes at a time. That implies that the exercise is not being performed to HIIT standards.
Let's take a look at several HIIT protocols:
1 minute on, 1 - 2 minutes off, repeat 6 times
30 seconds on, 90 seconds off, repeat 6 times
45 seconds on, 90 seconds off, repeat 6 times
20 seconds on, 40 seconds off, repeat 8 times
Note: Make sure to include a 5 minute warm-up and a 5 minute cool-down.
Notice that each protocol includes an "on" and "off" segment. These segments refer to intensity of effort and to correctly perform HIIT, during an "on" period you should be sprinting (or cycling, rowing, et al) at such an intensity that you reach a point of 'failure'. That is, you can simply no longer sprint (cycle, or row). You need to slow the rate of exercise to the "off" segment, which is your recovery period.
If done correctly, you will find that you will be hard-pressed to go beyond 20 to 25 minutes. Also keep in mind that as with any form of exercise, as your body adapts you will need to find ways to increase intensity to maintain the same intensity of effort level. This may mean increasing speed, include, and/or resistance.