Over the last six months, I've consistently given three pieces of advice to my students at SCCC: get comfortable with the Firebug debugger, contribute to open source, and learn to use Linux. The first is because all developers should learn how to debug properly. The second, because open source is a great way to start building a resume. And the last, in part, because Linux is what powers a large chunk of the web--not to mention a dizzying array of consumer devices. Someone who knows how to use an SSH shell and a few basic commands (including one of the stock editors, like vi or emacs) is never without tools--it may not be comfortable, but they can work anywhere, like Macgyver. It all comes back to Macgyver, eventually.
At Big Fish, in an effort to take this to its logical extreme, I've been working in Linux full-time (previously, I've used it either on the server or through a short-lived VM). It's been an interesting trip, especially after years of using mostly Windows desktops (with a smattering of Mac here and there). Using Linux exclusively for development plays to its strengths, which helps: no fighting with Wine to run games or audio software. Overall, I like it--but I'll also admit to being a little underwhelmed.
To get the bad parts out of the way: there are something like seven different install locations for programs, apparently chosen at random; making changes in the graphical configuration still involves arcane shell tricks, all of which will be undone in hilariously awful ways when you upgrade the OS; and Canonical seems intent on removing all the things that made Ubuntu familiar, like "menus" and "settings." I ended up switching to the XFCE window manager, which still makes me angry because A) I don't want to know anything about window managers, and B) it's still impossible to theme a Linux installation so that everything looks reasonably good. Want to consistently change the color of the window decorations for all of your programs? Good luck with that. XFCE is usable, and that's about all you can honestly say for it.
The best part of Linux by far is having a native web stack right out of the box, combined with a decent package manager for anything extra you might need. Installing scripting languages has always been a little bit of a hassle on Windows: even if the base package is easily installed, invariably you run into some essential library that's not made for the platform. Because these languages are first-class citizens on Linux, and because they're just an apt-get away, it opens up a whole new world of utility scripts and web tools.
I love combining a local server with a set of rich commmand-line utilities. Finally, I can easily use tools like the RequireJS optimizer, or throw together scripts to solve problems in my source, without having to switch between contexts. I can use all of my standard visual tools, like Eclipse or Sublime Text, without going through a download/upload cycle or figuring out how to fool them into working over SFTP. Native source control is another big deal: I've never bothered installing git on Windows, but on Linux it's almost too easy.
So there is one axis along which the development experience is markedly superior. It's not that Linux is better built (it has its fair share of potholes) so much as it's where people curently go to build neat tools, and then if we're lucky they bring them over to Windows. Microsoft is trying to fix this (see: their efforts to make NodeJS a first-class Windows platform), but it'll probably always be an uphill battle. The open-source developer culture just isn't there.
On the other hand, I was surprised by the cases where web development is actually worse on Linux compared to Windows. There's no visual FTP client that's anywhere near as good as WinSCP that I can find. The file managers are definitely clumsier than Explorer. Application launching, of all things, can be byzantine--there's no option to create a shortcut to an program, you have to manually assemble a .desktop file instead, and then XFCE will invariably position its window someplace utterly unhelpful. Don't even get me started on the configuration mess: say what you like about the registry, at least it's centralized.
None of these things are dealbreakers, the same way that it's not a dealbreaker for me to need GOW for a decent Windows command line. But if I was considering trying to dual-boot or switch to Linux as a work environment, instead of just keeping a headless VM around for when I need Ruby, I've given that up now. When all is said and done, I spend much of my time in either Eclipse or Firefox anyway, and they're the same no matter where you run them. I still believe strongly that developers should learn a little Linux--it's everywhere these days!--but you can be perfectly productive without living there full time. Ultimately, it's not how you build something, but what you build that matters.
If you do decide to give it a chance, here are a few tips that have made my life easier: