Tomoyo said:
How can anyone think the Sumerians are bad???
THEY ARE AGRICULTURAL!!!!! That alone makes them one of the best civs. Also, they UU is great. Although it can't upgrade the swordsman, I consider a big Warrior --> Sword gambit an exploit anyway. In an ancient war, Enkidus are the ultimate unit, right next to the Immortal and Mounted Warrior because of its cheapness.
If I was one of the people that appeared negative to Sum, please allow me to clear up the mess I made

In most epic games I play I'll choose Agr over most any other trait
combination so Sum is way up on my list as well.
However, my reservations about their UU still persist. I agree you get a lot of shields worth early in the game. It's still a defensive unit that upgrades to defensive units and even for a despotic GA it comes way too early. Maybe it's just a difference of playing styles. If you can get to Republic or Monarchy without using the Enkidu, you're better off with Sum than with 50% of the other agr civs...
Worse agr civs:
Azteca (Jag warrior): too early GA too, excellent if the map is very small or difficulty level is very low. Mil isn't among the best traits for me. Probably because it doesn't work that well together with Agr.
Inca (Chasqui scout): too expensive for its use imhso. Exp is the worst trait for me personally, I just can't get any luck popping huts

This is the worst of the Agr civs imhso.
Maya (Javelin thrower): probably a better UU than the Enkidu unless you've got horses nearby, in that case you're better off building horsies (in most games anyway). UU usefulness increases with barb activity. Traits are both nice and I've found they work ok together, although Agr have less of a problem building enough workers than other civs.
Better agr civs:
Iroq (Mounted warrior): top 5 UU, excellent trait combo and among the top 3 overall civs.
Celts (Gallics): another good trait combo and a powerful UU that has a nice window of opportunity between getting out of despo and the AI getting defenders that are better than spears; another top 3 civ.
Netherlands (Swiss merc): nice traits for most maps (- pangea), UU comes at the best possible time w/r to GA timing (ever did this: Get Feudalism, trade for Mono, kick off GA and enjoy your subsequent monopoly on Chivalry?

). Provided the map isn't pangea, top 3 civ.