Asus USB-BT400, Bluetooth 4.0

Does anyone know if Asus USB-BT400, Bluetooth 4 dongle works on Yosemite??

I'd like to know the answer to this as well.

It would seem it does. In my case the chipset version is 20702A3 and the firmware version is v14 c4096.
I haven't tried it it too many devices (a headset and a speaker mainly), and those work good anyway.
I used to have the firmwareuploader kext from osxlattitude project installed in ML, but with yosemite this particular adapter works out of the box which is nice.
Now, i couldn't tell you if handoff and continuity can be activated because frankly i'm not very interested in those features personally.
Anyway, attaching info from "system information":

Apple Bluetooth Software Version:4.3.2f6 15235 Hardware, Features, and Settings:
Name: My Mac Pro
Address: 5C-F3-70-65-08-3B
Bluetooth Low Energy Supported: Yes
Handoff Supported: No
Instant Hotspot Supported: No
Manufacturer: Broadcom
Transport: USB
Chipset: 20702A3
Firmware Version: v14 c4096
Bluetooth Power: On
Discoverable: Off
Connectable: Yes
Auto Seek Pointing: On
Remote wake: On
Vendor ID: 0x0B05
Product ID: 0x17CB
HCI Version: 0x6
HCI Revision: 0x1000
LMP Version: 0x6
LMP Subversion: 0x220E
Device Type (Major): Computer
Device Type (Complete): Mac Desktop
Composite Class Of Device: 0x380104
Device Class (Major): 0x01
Device Class (Minor): 0x01
Service Class: 0x1C0
Auto Seek Keyboard: On
Devices (Paired, Configured, etc.):
Philips SHB4000:
Address: 00-1E-7C-2A-86-37
Major Type: Audio
Minor Type: Headset
Services: Audio SNK, Hands-free unit, AVRCP CT, Headset unit
Paired: Yes
Configured: Yes
Connected: No
Manufacturer: Unknown (0x4, 0x115)
Firmware Version: 0x0115
Vendor ID: 0x0039
Product ID: 0x13A4
Class of Device: 0x04 0x01 0x240404
EDR Supported: Yes
eSCO Supported: Yes
SSP Supported: Yes
Services:
Bluetooth File Transfer:
When receiving items: Accept all without warning
State: Disabled
Bluetooth File Exchange:
When other items are accepted: Save to location
When receiving items: Accept all without warning
State: Disabled
Bluetooth Internet Sharing:
State: Disabled
Incoming Serial Ports:
Bluetooth-Incoming-Port:
RFCOMM Channel: 3
Requires Authentication: No
Outgoing Serial Ports:
Bluetooth-Modem:
Address:
RFCOMM Channel: 0
Requires Authentication: No

Click to expand...