Mt. Si is probably the most traveled trail in the state.  The proximity to major urban centers makes this trail popular for those seeking a good workout or preparing for more ambitious climbs. Don't expect to have a typical backcountry experience here but if your looking for a great workout and still want to be home with time to do house work this may be a good option.  While the scenery is subpar for most of the hike (compared to other North Cascades trails) there are nice views of Mt. Rainier and the Snoqualmie valley from the top.  

Mt. Si from North Bend.

The trees get smaller as you near the top.

Eventually you ascend above the tree line.

A view of the Snoqualmie valley below.

The Haystack Scramble should only be attempted by those sure of foot.  Most people stop at the base of this pyramid.  Those who make it to the top are rewarded with a splendid 360 degree view.