A lot of the suggestions already mentioned are good ones.. i'll just go over my own list.
1) Ad Group > Keywords tab: Ever use Easynews? Use it and copy their checkbox technique. I should be able to select ranges of checkboxes and update the bids in those checkboxes.
2) Ad Group > Keywords tab: Do I really need an Actions button with a dropdown when there is only one action? Rename that button delete and make it do just that.
3) Ad Group > Keywords tab: This may be a Firefox thing but why can't I copy and paste in the bid textbox? When I want to update a handful of bids, normally I would just copy and paste the value to save keystrokes. This problem would be fixed if you implemented #1.
4) Ad Group > Keywords tab: Get rid of Export to excel and just give me a plaintext list.
5) Ad Group > Ads tab: Add some kind of unique identifier for each ad. Ad Title is useless when I have multiple ads with the same title. This would really help me with matching up my tracking data with ads.
6) Ad Group > Ads tab: Why can't I change how many ads I can see at once? If I can only create 20 ads in a group, is it really necessary to have pagination? Let me just see all 20 ads. In fact, being able to select how many rows are displayed on all the datatables would be nice -- and have it remember!
7) Ad Group > Ads tab: Please, please add a character count to the Create Ad fields. It doesn't have to take into account dynamic variables, it doesn't even really have to do much of anything except let me know how many characters are in that box. It's not helpful to get an error message that says "You typed 97 characters but can only type 75". I have better things to do then count characters.
8) Tell me the time the performance data was updated, and not just the date. I don't know if this would be possible, but it'd be nice.
9) Fix UI/Backend problems. Each day I use adCenter is another day I experience randomness. Whether it is data not showing up, forms that stop working, or just plain bugs.
10) Speed things up. Why am I waiting ~30 seconds to do simple things like update a bid for a keyword? And more importantly, why is it not even telling me its doing anything? If I didn't have Firefox with Firebug it would just seem like Save was a button that doesn't do anything.
11) I know you guys love your .net. But seriously. Speed things up.
12) EVERYTHING takes forever.
When I first started using adcenter I found myself lost quite a few times, but now I'm used to it and like the way things are organized, for the most part. Someday adCenter might be good but for the time being its a distant third.
Oh, and also... please add a little bit of Opera support. I know Opera is sometimes a pain to develop for, but right now, I can't even login. I would tolerate only being able to view and not edit information.
Thanks.
Off-topic... my post didn't have any spacing... why did I have to add my own HTML [br] tags?