I prefer the Inspiron E1505. THe E1405 ( or 640M ) only has an integrated Intel GMA 950. This chip is very very bad if you plan to play games and to run AERO Glass Interface of Windows Vista. THis chip also steals memory from the system RAM so it slows down the machine.
I prefer the E1505 ( or 6400 ) with the ATi Mobility Radeon X1400. It is very nice for occasional gamming. This graphics chip is also Vista Capable certified.
Of course, you can run AERO Glass with the Intel Chip, but it will slow down the computer because the chip will need 224 MB of VRAM. The system will have less RAM so it will slow down.
What is your utilisation ? For an ultraportable, I recommend Sony ( even if they are overpriced ) because they have a hybrid graphics system : the Intel GMA 950 to save the battery, and the nVIDIA GeForce Go 7400 to have more fun in games and in a 3D environment.
There is also good IBM Lenovo computers with dedicated GPU.
If you want a 14.1", look at the Dell Latitude D620. I recommend it more than the 640M because it has the nVIDIA Quadro NVS GPU, a better GPU than the Intel chip, but for business. You lost 10 % of the gaming performances because it is an OPENGL oriented GPU, bu it still better than the Intel chip. The quality built of the latitude is also a little bit better than the Inspiron line.
Planning to buy the Inspiron 640M. Appreciate suggestions from current users, experts.