The fan design isn't anything new and looking around you see no extra power connector or CrossFire connector.
On the I/O side of things we've got a Dual-Link DVI connector alongside a HDMI and full size DisplayPort.
Looking at the specification side of things Stream Processors have dropped from 640 on the HD 7770 to 512 on the HD 7750. Textures units are also down from 40 to 32 while ROPS remains the same at 16.
On the core clock front we can see that's been reduced from 1000MHz (HD 7770) to 800MHz while the 1GB of GDDR5 sits on the same 128-bit memory bus and carries the same 4500MHz QDR memory clock.