I've always thought that lilies are dramatic in a vase, but I have only lately come to fully appreciate lilies as an integral part of the garden. By blooming about a week or so after the peonies and first flush of roses are finished, they fill a time slot in the unfolding fireworks of the garden. While the roses reload for their second round of bloom and the hermocallis are thinking about popping, lilies add pizazz and interest.
Lilies are easy and do not require a lot of attention. They don't attract pests or seem particularly bothered by mildew or other diseases. They can handle a bit of shade, as well as the sun.
One of the neatest things about lilies is that they require a relatively small footprint. A rose may take four feet or so, a peony at least three feet, but a lily only requires eight to twelve inches or so. But on this tiny foundation, depending on the variety, can arise a tower growing to four or six feet topped with huge, beautiful blooms. Their small footprint allows you to tuck them in just about anywhere.
There are only three downsides to lilies that I can tell. The first is that they do take a few years to get established. But gardening is not for those who cannot delay gratification! Roses take two years. Like peonies, lilies can take about three years to get going. This means waiting. I have been known to pinch buds before they flower to help direct more energy into development of the bulb.
A second down side is that some lily varieties need staking to keep them from falling over. You can take advantage of this tendency by planting them close to the deck and steps that attach to your house. You can then use the existing structure to provide support.
A final down side is that midway through their bloom, you can already start to wish that they would bloom A LOT LONGER. This feature can lead to addiction!