How was your overall experience for the swich to self-hosted ads in terms of time and money you had to invest given that the main sellingpoint for Adsense is its ease of use?
Getting an advertiser on board with your program is the hard part, swapping graphics in and out is the easy part.
The only time I've seen this is on my school's newspaper, and they are wildly unsuccessful.
Re: traffic spikes, no. There are limited spots which can be purchased so adding more spots whenever I want wouldn't seem right to my current advertisers who bought based on the limit in place.
Edit: I also get contacted by ad networks from time to time saying I could boost my revenue, but I always ask which advertisers they have who are relevant to my audience. It is always none. So at this point, I'm relatively confident that I don't need an ad network to service my particular niche.
The site is on Wordpress so I just use plugins to handle that stuff. I'm basically a publisher so Wordpress is perfect for almost anything I could need to do.