(I also like that the class names are hyphen-separated rather than camelCase, but that's a separate discussion ;)
Advantage #1 above is accomplished with a global clearfix of many elements, including <div>s (by default). For many sites, and certainly new sites, this is fine, but I was working on a site where Cascade Framework's global clearfix broke some of the existing CSS, so I wanted a standalone implementation.
The standalone implementation was relatively easy to implement; it simply requires wrapping each row with a class I added called "grid-row" (which is equivalent to OOCSS's "line" class). Example:
<div class="grid-row">
<div class="col width-1of2"><p>left column</p></div>
<div class="col width-1of2"><p>right column</p></div>
</div>
The good news is that the clearfix still works (thanks to the .grid-row class) so it's compatible with IE<=7 without needing to put a .lastCol class on the last column.
A similar implementation would of course be possible using the OOCSS class names (.line, .unit, etc.) instead.
Here's the link again to my standalone implementation of Cascade Framework grids, in case you missed it:
https://gist.github.com/mbrowne/6385935
I believe the grids should work just the same as with the full Cascade Framework as long as you include the .grid-row divs, but I haven't tested it all that thoroughly yet so let me know if you find a bug.
BTW, John has begun work on a SASS version of Cascade Framework. I noticed that the current OOCSS grids implementation provides an "ooGrid" SASS mixin. If anyone is interested I could possibly work on a similar mixin for this standalone grids implementation.