A WebmasterWorld thread reports that Google AdWords has added a method of choosing the ad delivery method you prefer. The two options include:
Standard: Show ads evenly over time Accelerated: Show ads as quickly as possible
Google has more details on this new campaign based setting here.
This option is automatically selected for you, and is best if you want your ads to reach a wide range of users over the course of the day. We'll spread your ad impressions across the day to make sure you don't accrue all of your clicks early on. However, if your budget is set below the system-recommended budget, your ads may not receive all possible impressions.
For example, if you want to spend US$30.00 over 30 days, your daily budget would be US$1.00. With standard delivery, your ads would appear throughout the day, from 12:00 a.m. to 11:59 p.m.. If your system-recommended daily budget is US$3.00, you may receive only one third of all impressions possible during that time.
Accelerated delivery This option is best if you want to increase the likelihood of spending your full budget each day. We'll display your ads as often as possible until your budget is reached. If your budget is set below the system-recommended budget, your ads may not receive all possible impressions.
For example, you might choose to spend US$30.00 over the next 30 days, with a daily budget of US$1.00. If your system-recommended daily budget is US$3.00, you may receive all possible impressions until your budget is reached. Therefore, you could spend your entire budget between 12:00 a.m. and 8:00 a.m.. In this case, your ads wouldn't appear again until 12:00 a.m. the next day.
Forum discussion at WebmasterWorld.