Tried out 4.0.1 with my hashfast babyjets with upgraded 0.4 preview firmware. I noticed now when a babyjet reconnects for any reason it will keep it's name (ex. HFB 0) in the cgminer window, but in the API it will get a new name (ex. HFB 14) instead of just reactivating the old name. It's not really high priority, but id help clean up the stats I'm pulling from the API if this was corrected.
Also, had a few cases were 4.0.1 crashed when a babyjet hit 90C, went back to 3.12.0 and this did not reoccur.
EDIT: Also, cpu usage by cgminer seems to have greatly increased. I noticed these things with two machines running Windows 7.