This is fixed in Arduino 1.0.1.

You'll need a newer version of the Arduino software.  I'd suggest the recent released 1.0.1, but I think anything newer than 0020 has Uno support. 

The Uno doesn't use the FTDI chip or drivers.  Select the top-level "drivers" folder, not the "FTDI Drivers" sub-folder, and Windows should be able to find the drivers and get the board working.

open_market: the Leonardo isn't supported under 1.0; you don't have to try 1.0.1 if you don't want, but that's the only version that supports the board.

FalconFour: thanks for all the information.  It's a good point about not starting an upload when the bootloader is already running; I'll add that to the getting started page for the Leonardo.  On the other hand, holding down the reset button should be okay (at least, it's always worked for me).  If I'm having problems uploading normally, I'll hold down the reset button, wait for the IDE to say "Uploading..." and then release the button.  Can you provide some more details about the problems you're having with holding the button down (e.g. when are you doing it, what exactly happens, which operating system you're using, etc)?

BTW, we expect the application (sketch) COM port to be different than the bootloader COM port.  The upload process takes that into account (it waits for the sketch COM port to disappear and for any new COM to appear, assuming it's the bootloader).  If you have better luck by forcing them to be the same, that sounds good to me.  Just wanted to let you know that it's not necessarily a problem that they have different numbers.

And yes, my guess is that KEY_F4 is an int, and so print() tries to print its digits rather than sending it as a single key press.  The write() function always tries to send a single key press (or a single byte, if you're using Serial).

In the future, we'd like to find a way to control which USB libraries / classes / capabilities are loaded in a sketch.  In particular, we'd like to avoid loading the HID (mouse and keyboard) support if you don't use it - allowing for other USB classes on those endpoints.  Currently, there's a Mouse.begin() and Keyboard.begin() function; ideally, if you didn't call those, the Mouse and Keyboard classes wouldn't be loaded (avoided both the flash and endpoint usage).  The hope is to change the core in the future to work that way.  We try to avoid using preferences in the boards.txt file to control things that aren't actually related to the board (otherwise, the number of boards needed would expand exponentially as you added preferences). 

As you say, CDC is used for the auto-reset, so we might not disable that by default.

Nick, I think it might be the opposite.  That is, the board is probably running at 16 MHz but the code is being compiled for 8 MHz.  So when you say Serial.begin(9600), you're actually getting 19200 baud. 

bigthunder, are you sure you have the right item selected in the boards menu?

What board are you using?  And what's the full name of the board menu item you have selected?

Also, definitely check out the troubleshooting guide.

The Mini comes with a bootloader on it and you should be able to get it to work without burning a new one.

You might try with Arduino 1.0.1 (just released).  We updated the avrdude programmer type used to upload the sketch to the Mini, which should make the auto-reset work more reliably.

Hmm, weird.  Is the TX LED lighting up before the L LED starts pulsing?  That would be strange because, as you guessed, the pulsing indicates that the bootloader is running.

Can you turn on verbose upload (in the Preferences dialog) and post the output of an unsuccessful upload?

FalconFour: what operating system are you on?  Do you see the RX and TX LEDs on the board flash when you try to upload?

Also, with the Leonardo, if you're going to use the reset button, you want to release it after the upload starts (after the IDE says "uploading..."). 

The Leonardo will be supported by the Arduino 1.0.1 software, which I'm in the process of building and releasing.  It should be up in a couple of hours.  (If it takes longer than that, it will have to wait until late tonight, because I'm flying back to Boston from Maker Faire this afternoon.)

The bootloader (and other details) of the Leonardo support in 1.0 have changed for the final Leonardo release.  The Leonardo won't work with 1.0.  I'll try to have 1.0.1 up ASAP!

Are you using an external clock with the ATtiny?  The internal clock is not always accurate enough for serial communication, even at low baud rates. 

Also, the SoftwareSerial library in Arduino 1.0 will work on the ATtiny, assuming you're running at 8 or 16 MHz (not 1 MHz).  In case you want to try a different serial library.

We're working on testing the bootloader here: https://github.com/arduino/Arduino-stk500v2-bootloader (there's a .hex file in goodHexFiles).  It fixes the !!! problem and watchdog problem, along with a few other bugs - all corrected by Mark Sproul.

I've seen occasional failures to upload with this new bootloader, but I'm having trouble reproducing them.  Any testing of this bootloader would be a big help, particularly on big sketches. 

Did you try the troubleshooting guide?  http://arduino.cc/en/Guide/Troubleshooting