I have worked on multiple large, enterprise-scale projects and MVVM was the KEY to keeping them scalable and maintianable. I can't imagine having separate design and development teams being able to work in true parallel without the workflow enabled by the pattern, nor would we have been able to have the team split between tiers, i.e. having someone code the WCF/service layer, another handle the view models, another work on persistence, etc, with unit tests to help with refactoring and even integration tests before other layers became available.
I didn't start with MVVM because it was a popular pattern, I selected it when I had to go to a massive Silverlight application and researched the best way to manage it.
Projects include a major social media networking tool for Microsoft called Looking Glass, the backend health monitoring system that ran the 2010 Vancouver Winter Olympics for Microsoft, a complex risk management SharePoint dashboard with Silverlight integration for PriceWaterhousecoopers, and the Blio reader (KNFB) that runs on both WPF and Silverlight. Those are just the ones I can talk about. Team sizes ranged from a few to dozens of developers and designers working simultaneously.
If people are having trouble scaling large projects with MVVM, or if it is slowing them down rather than speeding up delivery, they're simply doing it wrong.
I'd also say that if you are showing 100 fields on a single display, you might want to call in a design team because I don't know many humans who can process that much information at once. In databases with thousands of pieces of information, the beauty of Silverlight is mining and presenting that information in a way that the user is able to manage the information on screen in bite-sized chunks. Also, if you're manually loading those fields, again, you're just not taking advantage of the tools and patterns out there. On one project it took me 2 hours to build a generator that could spit out the base classes and then business logic was layered on top. A short investment up front for faster development on the back end.
Typical rule: if you're repeating the same thing hundreds of times, go find a tool or build one to automate it.