I like to hike in the national parks and use Trails Illustrated maps when they are available. Trail books often have small maps of the trails they describe, and those maps are fine for short hikes, but it's a good idea to have a larger topographic map for longer hikes. TI maps are durable and have a water resistant coating. (Good for when you get caught in the rain; probably less so if you fall in a creek.) TI maps mark the trails and their topographic features. The elevation markings give you a good idea of how steep a portion of a trail is. I've used TI's Glacier/Waterton map for several trails and always found them to be accurate and helpful.
I recently purchased this 2004 revision. Unfolded, the map paper is the same size as the 2000 revision, but feels substantially heavier. The park map, however, is now a bit bigger and is split with the north half of the park on one side and the south on the other (with a generous overlap between the two). The written information about the park that was previously on the back is still present, but is reduced in size and located in several smaller boxes spread around the map. An improved feature of this revision is the inclusion of more area beyond the park boundaries. A bit more area is covered on the west side of Waterton, but a lot more area is covered to the south and west of Glacier. This includes the area between Whitefish Lake, Columbia Falls, and Kalispell, as well as the Flathead National Forest and the Great Bear Wilderness. I don't use it, but this version indicates that it is GPS compatible with a full UTM grid.
TI's Glacier/Waterton map is worth having if you plan to do any hikes longer than a few miles. The 2004 revision is a good buy, particularly if you have an older version that is showing some wear. If your older revision is in good shape (they are durable after all!) you can probably get by with it.