In reviewing an AMCAS application I actually spend the most time on the experiences (employment/activities) section. My rationale is that your metrics are easy to interpret and your butler may have written your personal statement, but the experiences you list shows me two important things: (1) what you have chosen to do with your available time, and (2) what you consider worth sharing.
Here's a little exercise. Lay out your proposed experience list in order of descending hours, the look at the list and try to see what it says about you. For example, if your list looks something like this (which is only a slight exaggeration):
1. Hobbies - Skiing/snowboarding, 9000 hours
2. Hobbies - Windsurfing, 7000 hours
3. Hobbies - Cycling (road and mountain), 5000 hours
4. Hobbies - Rock climbing, 2000 hours
5. Research, 100 hours
6. Shadowing, 20 hours
7. Habitat for Humanity, 8 hours
...it tells me that you are a very active, outdoorsy kind of person. Great. Good for you. It also tells me that you are more concerned with enjoying yourself than getting into medical school. Not so great. Bad for you.
A couple more easy rules to follow:
(1) If you have five or fewer entries don't apply. If you have 12 or more check for excessive filler.
(2) Don't list anything from high school or earlier. I don't care if you played for the state championship football team. I don't care if you had great accomplishments as a boy scout. I don't care if you were valedictorian of your high school. Pretend your life started on the first day of college.
(3) Don't include anything that is considered a normal part of existence for decent human beings. I have seen people list the deaths of relatives/friends in this section. If that event impacted your journey to medicine do yourself a favor and put it in the personal statement. I have seen people list being a husband/wife/father/mother/sister/brother/son/daughter/best friend in their experiences section. I can feel the earnestness oozing through the computer screen when I read these, but it doesn't make you look appealing. At best, it makes you look like a newborn fawn that just hobbled into traffic.
(4) In writing the entries I know there is an endless debate over being explanatory versus being brief, so you need to walk the line and be concise. That means you explain wherever necessary, and don't explain where it is unnecessary. Use enough words to get the point across and then stop. Tell what you learned only if you have something worthwhile to tell.
A good example is a poster presentation. Most everyone in medicine is familiar with posters. We know the drill. It is perfectly fine to simply list that you presented Poster X at Conference Y on date Z. You don't need to wax poetic about how crafting this poster taught you the value of teamwork and the true meaning of Christmas.
Now, if you have done something that is likely unfamiliar to the audience, like worked as a counselor at a camp that serves a specialized population, that deserves some verbiage.