It takes a long time to hike up to the lake, but is well worth it when you get to the top. Make sure you take the 5mins detours to see Barrier Lookout on the way up or down.
The trail is intermediate. Allow 3 hours to hike it up, and 2 hours to "run downhill". Once you complete the first 6.5 km, you are done with the difficult zic-zac, enjoy the scenic glacier lake:)