How far along were you before you started to use these? I felt guilty parking in them for the longest time! I thought that if I'm perfectly capable of walking a couple extra steps and allowing the space to be free for a pregnant women who is 8 or 9 month's pregnant, with multiples, or a high risk pregnancy the better.
Today I went shopping and simply didn't feel like walking more than I had to, so I used it - while at 33 weeks pregnant. I thought I deserved it by this point in the pregnancy though!