All the current mods do is flash the firmware of the DVD player, the chips just make it so can turn this "off" so you don't have to worry about re-flashing to play on xbox live, or when you want to rip games, etc.
As it stands, the console is still region locked. Some games however are multi-region by default. This why you can play them. Nor is it possible currently to patch the region manually, since the all the mods do is disable the DVD check, the console still checks for signed code, and if you change the code you'd have to recertify it.
What all of this means is that in the USA you will have two options:
1) buy import games.
2) mod your system and download and burn PAL games.
Of the two options, 1) is probably fair easier, if you're not technically minded.
Should you need to get your machine chipped and you're not sure how, this place:
http://www.konsolen-tuning.de/ is very good, and they're local, I can vouch for their services

They do both walk in or mail order.