Originally Posted by FBinNY

Rims with eyelets are neither better nor worse than rims without eyelets.

Granted that all things being equal, eyelets improve the strength of rims by spreading the nipple load, but all things aren't equal. Manufacturers factor whether they're using eyelets or not into the design of the rim and rims without eyelets usually have thicker sections along the belly to compensate.

Eyelets can also help by making a better seat for the nipples, but that can also be done with nipple washers if desired.

There is one other way that eyelets help, especially for those who ride in the rain, or live near a coast. Rims are drilled after anodizing, so the wall of the nipple hole is bare unprotected metal. When ridden in the wet water gets in there and sets up a corrosion process, which is much worse if salt is present. Over time this can freeze nipples in the rim making re-alignment impossible, and later yet lead to stress cracking in the rim. A simple preventative is to apply a drop of waxy oil, like LPS-3, or Boeshield to each hole and let it wick in.

Probably the single most important benefit of eyelets is cost and time savings. Machine applied eyelets in rims is a cost effective way to save time when building wheels in production.