When working on MacOS 8.x (not sure which point release), they surveyed users, and their number one complaint was boot time. It took long for the system to boot (around 45s on average at the time). They looked into it but also asked the question, why do people care about boot times at all? At this point, the systems were capable of sleeping, so reboots should be rare.
They found that people were rebooting because of instability, not just once a day or once a week. While they did improve the boot times, they put more effort into making the OS more stable. When the new release shipped, people stopped complaining about boot time, but not because it was vastly improved, instead because they were doing it less often.
The moral of the story is to make sure you understand both what your customers are asking for and why your customers are asking for it.