Yes, I'm using my personal laptop for travel and keeping the company machine at home as a "spare". My personal machine has a better wireless card (Intel A/B/G), a bigger disk (80GB vs. 40 GB), a faster processor (2 GHz vs. 1.83 GHz), and a CD-RW DVD-RW instead of a CD-RW DVD-ROM, but less memory (1 GB rather than 1.5GB).
The optical drives (DVD-RW vs. DVD-ROM) are swapable and in fact I've just picked up another CD-RW / DVD-RW on Ebay for about $35 plus $15 shipping on Ebay rather than the Dell price of $229. This way we can back things up at home even when I am on the road.
I suspect the memory may be swapable too. The M20 uses 533 MHz DDR2 IIRC. I haven't bothered to figure out what "my" 610 uses. The one Dell has for sale on the outlet site seems to use 533 MHz. (And it looks like a good deal at $879, much better than the company got; maybe I should get it for my Dad.) So, the memory is probably swapable. On the other hand, I'm pretty sure that the 1 GB I have in the M20 is enough for what I am doing and the 1.5 GB in the 610 is probably overkill. (I saw no noticeable speedup when I upgraded from 512 MB to 1 GB) earlier this year.)
I'm not sure if it is weirder that my machine was purchased in September of 2005 while the company machine was purchased in June of 2006 or that the machines cost about the same. OK, the company machine may have been a couple of hundred dollars cheaper (as in $2k vs. $2.5k). But I still think the company got ripped off especially since the D620 is out already.