Google has recently updated their user interface for Adwords users. If you are looking for a quick answer, I like it so far. I have also talked to a few other SEM professionals and the general consensus has been, "Well, it seems to be an improvement. But no matter how you look at it, the Adwords UI is still better than anything Yahoo! or MSN has to offer!" I think we can all agree there.
First, efficiency has greatly improved. It is easier to access everything without traveling to separate pages. For example, I can easily edit bids, keywords, and ads for campaign A and with a click of a button I can move to campaign Z. Another nice feature is being able to access all keywords and ads by campaign, instead of only by ad group. Also, the ability to change campaign settings is easily accessible from the campaign view without venturing too far from everything else you were doing. I have also found some new reporting features, additions to campaign settings, easier access to Analytics, and couple more things here and there. Overall, usability and efficiency gets an A in my book.
One thing I don't like is the automatic selection of ad serving to mobile devices. If you upload your campaign through Adwords Editor, it automatically chooses to show your ads to iPhones and other mobile devices. You have to go in the the UI to remove this selection. I never run campaigns to mobile devices unless they are optimized for mobile devices. You will see much better performance if you create a campaign which includes keywords, ads, and landing pages that cater to these devices. Google did include the option to duplicate campaign settings if you start your new campaign through the UI, another nice feature which can alleviate this problem for the most part.
You will have to try the new UI out for yourself to come up with your own opinion. You can also check out some of the material directly from Google for more information. Again, overall I am pleased. It may not be the prettiest thing out there, but if it makes my job more efficient I am happy!