I develop apps plus web-service backends (mostly in PHP). Some of my "apps" are designed to run as apps on phones/tablets and as Chrome plugins (or just webpages) on desktop/laptop systems.
I currently use JetBrains PHPStorm (buggy, and service isn't great, but it hassome cool IDE features and reasonably priced) and Eclipse together. In Eclipse, I have Aptana plus web tools platform, and of course the Android ADT plugins installed.
I've got another guy who does builds/plugins for iOS using a Mac/Xcode/etc.
We try to do as much debugging in browsers as we possibly can and just use the simulator/emulator (and devices) for testing plugins and other device-specific stuff.
We're just moving to PhoneGap 3 and are evaluating PhoneGap build as an alternative. (We're particularly interested in the debug capabilities. It's not clear how much they really add over what's already out there.)
It certainly sounds good on paper, but we'll have to see.
If you're doing plugin development, you'll need the appropriate system for development (PC or Mac) and testing.