Pros
The people are the strength at Ames. I've been to several centers and the Ames campus has a lot of really interesting staff with diverse interests outside the workplace. The campus is large, plenty of trees and room to run. The workforce is older, but the number of 20 & 30 somethings has radically jumped in the last few years. There are some good fringe benefits - gym, child care center, happy hours, etc. The upper management is some of the best I've seen at NASA, in that they seem to be technically savvy and have a general consideration for their employees. Ames is also of the more innovative NASA centers, really pushing the envelope within the agency. It's a small pond - if you are technically capable you can jump right in and make an impact.
Kontras
The work is fun, interesting, but often only moderately inspiring - the flagship projects go to larger centers. The center has a culture of subcontracting challenging, detailed designs, which is fine if you're a systems engineer, or project manager, but not if you're a design engineer. The large numbers of scientists mean that Ames hits the senior-level quota very quickly, leaving little room for engineers to get promoted. This quota is set by HQ and Congress, indirectly. Promotion criteria can be a bit flimsy.