I'm also trying to take the step over to reflow but as a designer I'm feeling restricted by the current grid support... A vertical baseline grid is something I always use to make sure rhythmic and even spacing in my designs. This is the kind of spacing I'm setting out to achieve:
http://blog.weare1910.com/post/88576778651/between-the-lines
Indesign is actually really close to being a great web-layout program... Except it's not very easy to design responsive layouts...
EDIT: found a possible workaround for creating a baseline grid inspired by this css code: http://jsfiddle.net/gehrmannDesign/82T7R/
It's not possible to position gradient backgrounds in reflow, however, I created an 1x1 px svg-image in illustrator with a really thin vertical line (0.05 px wide) and added it as an background image for the entire document. Now, by changing the background scale to the default line-height I get the baseline I'm looking for.
Not too intuitive but it works! Now I'll just have to try out Reflow for real and see if I can actually use it in production :-p
Result:
