As an example of the frustrating process of learning software by the trial-and-error method, it turns out that you CAN save multiple versions of an image to your shoots, and without having the storage overhead of multiple copies of the raw file.
I was lamenting the same inability til I learned in the Adobe Labs forum how to use the History tab in Develop module to save and name different versions of the same image.
Granted you can create multiple history states, but that isn't a easy as in Aperture, and the implementation isn't as smooth. Also in Aperture there isn't a big penalty storage vise as the versions are just sets of data and scripts/adjustments. A version isn't a complete copy of the full file. They only add a few kb each.
Also a killer problem for me was that Lightroom doesn't like REALLY large files since like Beta 2/3, I shoot a few images and stitch them together and have files that are regularly 200-400mb, Lightroom won't import them. Aperture will.
There was something on the lightroom support site saying that as it was aimed at DSLR users and the like they don't provide support for huge files, as no current digital camera makes files that big.
Maybee this has changed recently, but certainly wehn Beta 4 came out it wouldn't support large files. Perhaps Beta 4.1 changed that?