1080p24 at Pro Res Proxy resolution is only about 25% bigger (in terms of data rate) than DV. What's great about proxy editing these days (as opposed to using SD or even DVCPro of just a few years ago) is that we have options like Pro Res Proxy and Avid's DNxHD 36 which give us full raster, low-bit rate codecs that won't strain a machine like H.264 will. Being full raster is the best part, IMO, because any graphics you make or moves you do on the footage will translate perfectly from your full raster offline edit to your full raster online edit. If you aren't using a full raster proxy then all of your graphic elements and moves on the footage will all have to be redone (which sucks).