I'm not sure what your point is exactly. At the base price, I still don't see how the XPSM1330 is a "MacBook killer"; how does the form factor kill it? I might be missing something but how does the XPSm1330 form factor kill it? For the kinds of stuff people use it for, what difference does Santa Rosa make? GMAX3100 graphics are somewhat better than GMA950, but still terrible. Once you start configuring it up with an 8400M GS, etc. , it gets to be a lot more expensive than a MacBook anyway.
Regarding the Inspiron line, again, so what? You can get a MBP with an 8600MGT with 256MB of VRAM as well. I won't go into detail on this again, but the Inspiron 1520 has a lot of glaring weaknesses compared to the MBP as well (6.4 pounds is pretty heavy, it's much thicker, etc.).
What's your point then exactly?