I'm at 100% this year. Last year I only missed two. Putting aside the SWU's which I've used for TATL travel, I was upgraded at the 6 day window all but three times, and didn't have to play the gate lottery at all.
Here are some suggestions to improve your upgrade percentage:
1. If possible stay out of Atlanta, you have better UG chances at MSP, CVG and SLC.
2. Try to pick 757 aircraft as much as possible, occasionally going to ATL via 757 and connecting for another 757 (you may end up with a two-three hour layover in the SC, which frankly can be relaxing and allow you to get some work done).
3. Fly early or late. I often try to grab 6 am, or 8 pm flights. Try not to fly at peak times 7-9 am or 4-6 pm.
4. Stay away from Thursday, Friday, Sunday or Monday. That is when most business travel occurs. Tuesday and Wednesday are best and Saturday's are mostly leisure travelers. Even when I am on business, I will ocassionally choose an early morning Saturday flight than battle Friday afternoons at the airport.
5. If you are flying over 1500 miles, buy a K fare and ug with 12.5K. As a PM, you will earn about 200,000 miles per year. Giving back 70-80K is no big deal. If you have AMEX, you will earn even more. By way of example, if I buy a K fare for say $250, and fly 2000 miles on the trip, I will earn 4500 miles, thus the UG only costs me 8000 miles. This is best saved for holiday weeks, Friday, Sunday and Monday travel.
6. SDC.
7. For holiday travel, look for A fares, which occasionally can be found for less than an M fare. (I didn't purchase any this year).
8. Learn the routes that are light on Medallions. For example, PBI is very Medallion heavy, as DL operates the largest schedule there. Wealthy Palm Beachers often pay First, so on peak days, there are very few seats available. FLL on the other hand is a larger airport with much more competition and therefore has fewer Medallions per available seat than PBI.