Received my F5 and got it mounted yesterday. Here's my comparison to the F4 that I ran for a few years.
+There's a witch in there who runs the thing with voice prompts - this is sort of handy.
+Don't have to hold a button for a full 2-seconds to fast forward songs like with the F4, now it is one quick tap on the up or down buttons.
+FM tuner is pretty awesome. It's fiddly to scan and set into memory the stations, but it's a nice option once set-up. 8 presets allowed.
+Unit can be updated online like the Sena's now.
+Unit has a new aux. audio input - though I doubt I'll ever use it.
+Separate volume controls for each device allows different levels to be kept.
+Paired with my iPhone 4S and my wife's F4 easily. It will pair with the F3 as well.
+The witch tells you at each start up how the battery is doing. This should take out the guess work of how much charge is remaining.
+New mic/speaker connector is more robust and has a sliding metal mount for stronger connection.
+Water resistant just like the F4.
+New boom mic has the word "Mic" written on it so you can tell if the mic is actually facing your mouth properly.
+Pairs with more than one other unit - I think it was six total, and you can dial up individual units or the whole group.
+Text to Speech - I haven't figured that one out yet but it sounds cool.
+Comes with boom mic and full-face helmet stick on mic, as well as two sets of matching speakers for either option.
-Phone answering is not one-touch anymore, unless you turn off the voice activation.
-The witch with the voice prompts is always calling out the menu options when using the buttons - she can be cut short by remembering the sequence of buttons needed and pressing them before she starts talking.
-I had some trouble returning to the music after a phone call - it may be just learning curve.
-To activate the music with the F4, it was a double tap on the main button. With the F5 I have to surf thru the menu items to find streaming music, press once to activate that menu item, then hold 2-second until a beep (which is not that audible at speed) to play/pause the stream.
-The device is reversed from the F4, with the main button toward the front instead of the rear of the device. This is just a learning curve.
-There is no big chart with the device that tells you the secret art of using the buttons. Instead it relies on the witch voice controls. This is not a big negative, just a difference.
Because of my helmet's set-up (HJC Symax II), I had to mount the device pretty far back on the helmet to avoid the flip-up part. On my F4 I installed it on the flip-up portion of the helmet, and I think that is what killed that device. When the flip-up is flipped down quickly, it eventually caused the mic/speaker connector to fall apart. Lesson learned!
Overall I give it a big thumbs up.