I agree totally. For myself, I've got to have the option there to upgrade everything, and until they start putting 64 meg GeForce2 chips on as onboard video, I can't see myself considering that option.
When building computers for friends and family, however, the onboard options are great. For $200 (Canadian) you can get the mainboard, audio and video taken care of. The last machine I put together I had that with a Duron 700, 128 MB of ram, 10 GB harddrive and a 56K modem, and with the basics scavenged from her 486 SX, built her a computer that will do more than she needs and last her for years for under $600 bucks. (again, Canadian.)
So, you can save about $100, but your gaming and high end will suffer. If this is not an issue, by all means go for it.