Very true, a bigger screen, keyboard and mouse does make a difference, but I'm thinking more about the hassle factor of two machines as I see it.

Two machines = PITA. When an external monitor and keyboard take care of ergonomic problems of solely using a notebook, what's the holdup?

The only advantage to two machines is redundancy - if something happens to the notebook (theft, droppage, etc.) you're up an running with the desktop. However, you have to invest in a good sync utility (I use You Synchronize to sync between my PB and a windows desktop) and network the two machines in order to make it seamless (thumbdrive? you've got better things to do with your life). But you're right - the whole issue of email and PI is the dealbreaker.

zzgavin,

Let me add that the things I need to synchronize I handle in various ways. (I work in a government office on government computers during the day and my home computer at night.) Anything that comes via the 'Net stays on the net. That means my email, bookmarks, etc. are all online. For example I use linkaGoGo for my bookmarks. I use GoDaddy's Online File Folder for my online files. I also have a CryptoStick thumbdrive that allows me to run MS IE off of the thumbdrive so all favorites, temp files, cookies, etc are on my thrumbdrive. I also run Portable Firefox with an [url=http://extensionroom.mozdev.org/more-info/booksync">extension to sync my bookmarks via FTP every startup and shutdown of Firefox. I even have a thumbdrive with my source code files on using subversion. I check them out to my work computers, check them back in when I leave, and then check them out again on my home computers. With this sytem I can use any Windows computer with an internet connection (keeping in mind keyloggers).

Another way to think about things is a client/server sort of arrangement, assuming you can access that desktop from outside the office, with the laptop accessing the desktop as if it were a server. Or, if you're comfortable with CLI tools, syncing stuff up is a snap.