It’s been a while since the mbed was introduced, and I haven’t personally taken a look at it since I bought my first unit a couple years ago. One feature of the mbed that initially dissuaded me from using it more around the office was the online IDE and toolchain. I once had a quick, two week prototyping effort totally thrown off schedule when the mbed website went down for a compiler upgrade on exactly the wrong day.
I was just checking out the mbed again recently, and I’m happy to report that the libraries (the most powerful feature of the mbed platform) fully support offline compilation! A number of compilers are supported, including several free ones. The mbed team has put together a nice set of instructions for migrating your existing mbed projects to an offline tool chain. And, if you’re like me and prefer to use a fully-featured IDE, you can even use Eclipse for your mbed development.
For those not familiar with the mbed, it’s worth knowing about. It’s more than just another microcontroller prototyping platform. The large collection of existing code makes it easy to quickly assemble systems with advanced functionality, i.e. emulating a USB keyboard, posting a tweet, checking a POP3 email account, playing audio, reading from an SD card, etc.