Very useful discussion. I have a need for more space on / and would prefer not to have to softlink directories to other partitions, so this is very useful.
I usually do a flashall.sh -b, which has the same effect as doing a recovery then flash, so it's all done in one step (re-partitioning and flashing).
One downside worth noting though, is that increasing the size of the / partition will increase the size of the ext4 file, which takes longer to flash. Not too bad, but takes quite a while with 2Gig plus root partitions
Rgds,
Dave.