Installing Android ROM on a HTC HD2 on the SD card - Performance impact?

I'm currently running Android on my HD2 using the internal memory. However I'm having terrible issues with the memory filling up and I can't seem to solve it. I considered installing Android directly onto the SD card, but was told by a friend that it would slow down the OS so bad that it would hardly be possible to use. So my question here is quite simply; will there be much performance impact by running Android from an SD card? --- Adding bounty now, due to lack of patience. * I'm looking for an answer derived from personal experience or believable online sources * I won't accept probablies and maybes