Lightroom 4 question

In use a similar setup--laptop with external HDD for images storage--and usually use a 24" monitor and separate keyboard when I'm at home. One advantage in having the catalog on the laptop is that previews of your images are stored in the catalog. While you can't use the Develop module without access to the HDD, you can still add keywords, sort images, geolocate, etc. so this may be useful.

Stuart