Work from external FW 800 drive?

My one year old MBP is quickly running out of storage space primarily from images. My preference would be to store all image files on a external firewire 800 drive including working on the images through the Lightroom catalog. Has anyone every used an external firewire 800 drive as a working drive through Lightroom? Impressions? I understand the work will be slower than from the internal 7200 RMP drive but did you have any unforeseen issues?
Thanks

Have been using FW 800 for back ups since Panther and even booting the Mac off the Ext HD while running Leopard < much larger HD footprint that Snow Leopard > was a little slower but nothing drastic, probably around 30 secs slower. Both main drive and Ext HD were 7200s