Went out this evening for a 4 mile run based solely on feel. Ran without my GPS watch and only with my Blackberry GPS going announcing the mile markers, but not the time intentionally.
I started off with a warmup mile and then sped it up a bit. I ran to what I thought was about 2 miles (music was too loud and missed the 2 mile announcement) and turned around. The 2 miles back was much faster than on the way out with the last mile the fastest..... and with the biggest hills (go figure).
The run turned out absolutely awesome, and felt great. The only place I felt overly fatigued was near the top of the hill at about 3.5 miles. You can see why by looking at the elevation of my run (which also shows my pace) by clicking here: http://bit.ly/cabKAl