Hi Heidi,
I've been mostly walking for exercise this summer. I started out training for a triathlon and then aggravated a herniated disc in my back, so switched from running/swimming/biking to walking and physical therapy exercises. Right after the injury, I was losing weight at the same rate that I was while training, 1.5-2 lbs a week. Now things have slowed down some, in part because I starting eating a bit more and walking less, but I'm still losing about a pound a week. Which would work out to 15 pounds in four months, rather than a year.
At first I was walking a mile at a time 3-4 times a day, and now I'm walking 3 miles to work. Sometimes I walk round trip, but usually I'll take the bus or my car one way. Because I've been heading to work, I been going about 3.5mi/hr, which for me is less that a true exercise pace - my heart rate doesn't go up and I don't start to sweat (except from the heat!) So I think I should start incorporating more walks home and make those more oriented towards cardiovascular effort. One thing I've read that has been helpful is that you can incorporate intervals into walking - alternating periods of intense effort with periods of less effort. It's hard for me to imagine wanting to walk fast for the bus for my entire 50 minute walk, but I could rush to an imaginary bus for 5 minutes and then walk more slowly for a bit and then rush to that bus again.
So, yes, absolutely, do the exercise you like to do and it will help you lose weight faster. I would say though, that the core strengthening exercises that I've been doing (yoga before the injury, physical therapy since) have been very helpful. I had a similar injury last year, and I've recovered much more quickly this time, and having strong abs and back muscles will help prevent more problems in the future. And I have an identical twin sister, and we're about the same weight now, but we noticed when I saw her last week that I was a bit more "toned" around the mid-section, making my weight loss more visible. So adding some kind of core work or possibly weight training, could both help you in terms of health and staying active, and in speeding along and making your weight loss more apparent. Yoga or pilates or some kind of core focused exercise video would work.
But don't let that suggestion get in the way of walking - if you like to walk, and other forms of exercise aren't appealing, just start walking! You can always incorporate something else later, if you decide you want to. I was losing my focus on walking, so now I've started posting to the walk/run thread - it's really fun to have a goal and keep track of how much I've achieved.