The sub handling has gone to hell for me. So far I've only tested it with the 688i, but it takes the sub FOREVER to change depth. Literally it dives 1 ft per every 5-10 seconds. At best that works out to a 20 minute descent to 250 feet.
The acceleration is FUBAR as well, going from 0 knots (ice surfacing) to 5 knots didn't work at all. Only managed to get it up to 5 by ordering flank speed and then stopping the dial once it hit 5.