The western part of the trail (from the North Bend to the Columbia, across the Cascade mountains) is in very good shape. The most scenic and pleasant part of the trail from North Bend to Thorp is amazing. It includes the 2.1 mile Snoqualmie Tunnel, which is exciting the first time you try it. The section through the Yakima River Canyon is my favorite.
The eastern part (from the Columbia to Idaho) is pretty rough and a few small pieces are missing, but a road detour for a mile or two is probably a welcome change from the endless trail.
A few years ago, some state representatives conspired to give away the eastern half of the trail to private land owners, but their own incompetence doomed this attempted theft of public land. The law, as written and passed, specified a section of the trail that had a length of 0. But it attracted enough attention and outrage, and as a result, there is now more of a budget for maintaining the trail.