If you're playing in a standard wealth-by-level game, you'll be able to get the same bonuses that the Vow provides by buying them in item form. The bonus feats are kind of shiny, but you run out of useful ones after a couple of levels. Vow of Poverty does not make monks awesome. Vow of Poverty makes Monks (and other characters) that don't own any items, suck less.

There's only one situation where it makes mechanical sense: if you're playing in a low-wealth or low-magic-item campaign.