More to add to the United program:

Positives:
- Lots of airline partners.
- Star Alliance and Star Gold.

Negatives:
- No changes of any kind on many of their airline partners after departure.
- Rules for mileage accrual on code-share flights are very confusing. I wish they would just treat them like a UA flight just like most other airlines do.
- No elite bonus when travelling on alliance partners.

Great story idea. I'm probably deep in the Amen Chorus on a few of these aspects by now, but if it's votes that count, here's mine:

CONTINENTAL (plat):

Best: 1. Domestic upgrade policy
2. frequent lump-sum mileage specials
3. they don't starve you in first class
4. good chance of great mileage sales
5. a 125% platinum bonus

Worst: 1. EasyPass as a "solution" to stingy seat allocations
2. Bonuses apply only to actual miles rather than 500 minimum
3. Regional-jet substitution making upgrades meaningless on more routes
4. Website mileage crediting delayed or confusing.

DELTA (FORMER gold)

BEST:

1. Website mileage credits almost in real time.
2. More of a can-do attitude in booking award travel over the phone.

WORST:

1. LUser fares (made me leave!)
2. Service cutbacks - even the "turkey twinkie" was too expensive. Cheap, cheap, cheap

NORTHWEST (member)

BEST:

1. Patterned after OnePass
2. Good range of partners and exotic destinations

WORST

1. No-mileage Cyberfares indicate NW management not as committed to a good FF program as Continental is.
2. Miles + $$ specials a good idea, but again no mileage credit. If I'm paying $100 or $200 I want MILES! NW management wants customers to bargain those away.