A couple of months back while running either CyanogenMod or Savaged-Zen on my HTC EVO, I ran across the then-bug of extremely slow file transfer rates via USB.
Since I use my EVO to move gigabytes of data to and from work just about every day, this issue meant there were no quick "Oh, I forgot that database, let me do a quick copy and head out the door." Instead it was "Oh, I better find a DVD-ROM because this is going to take forever."
Dual Mount SD Widget was reported to be one of the solutions back then and at the time, I purchased it ($0.99 in the Market) simply to be able to copy files over at normal speeds to my 32GB microsd card. The app does a great job at this, but now I use it every day for a different reason.
Dual Mount SD Widget allows mounting of your EVO without having to unmount your SD card from the operating system. What this means is that you don't have to sacrifice your ability to run apps you moved to the card in order to copy that 300MB episode of "Doctor Who" over for the gym. Gone are the wait times for the EVO to notify all the programs that they have to shut down and vacate memory so that it can be mounted.
It plays nice with every EVO ROM I've run in the past couple of months too and has become a welcomed tool in my arsenal. Check it out at the links below.