Error reporting much improved. You should now see line numbers on runtime errors.
Fixed rate sampling API allows analog inputs to be sampled at regular fixed intervals (eg for audio), see API docs.
Low power WiFi mode implemented; use imp.setpowersave() to enable (more info on API docs page)
imp.onidle() added, allowing a task to be run when the imp is otherwise idle. server.sleepfor()/server.sleepuntil() calls should only be called from imp.onidle(), and you'll get a warning if you don't.
pinx.read() will read pin level for all setups apart from analog. You can check a UART line level even if the pin is still configured as a UART, for example.
BSON fixes which mean, amongst other things, that persistent stores work better with tables.
More squirrel strings stored in flash, freeing up some RAM space.
uart.write() now accepts strings and blobs, in addition to integers.
Green LED will stop flashing after 60 seconds. When the light is off, the imp is no longer listening for blinkup and hence can enter a lower power state. Note that if you want to BlinkUp and imp, you need to do it within 60 seconds of power up.