I've had my Scala G4 for about 4 months. Me and a friend got them for a trip we did in June. Version at the time was 2.2. Its nice to have firmware upgrades, but as a designer I know companies tend to release products earlier then they should when they are firmware upgradeable. That is the case with the G4. I use a Zumo paired to the G4 and the Zumo 660 is also paired to my iPhone. This three way connection is pretty buggy. When the G4 was upgraded to 2.3 and the Zumo went to 3.9, things got better, but only marginally.
Where it really falls short is my buddy and I intercomming while listening to A2DP music. All of these mixed together caused many problems throughout the day. We each had to power the units off and back on at least 10 times a day.
I think the thing that bothers me the most is how long the intercom takes to connect. If you are in the garage next to each other the intercom takes about 3 seconds to connect. On the road with some distance between each other its consistently 8 seconds. Another friend has bought a unit since our June trip and connections to him are similar.
That being said, once the intercom connections are made, the quality of voice over the intercom is pretty good. The system does a VERY good job of blocking out wind and motor noise. Cell phone callers rarely can tell I'm on my bike. They usually just think I've got them on speaker phone at home. VOX is completely useless. You have to yell very loud to get it to connect. Most reviews I've read said the same thing.
My experience with their tech support wasn't good either. First I tried e-mailing them a tech support question. I waited 17 days and finally they e-mail response was "call us about this issue". Thanks. 17 days to tell me to phone you. But what really peaved me was a problem that kept happening with my buddy. The button that connects intercom channel A to both riders is the same button as connecting to A2DP audio (his blackberry's MP3 player). For intercom you press for 1 second and for A2DP you press for 3 seconds. When we were done with conversations he'd try to go directly back to A2DP connection, but the unit wants you to disconnect intercom then go to A2DP. Everytime he did this he'd not only lock up his unit, but it would lock mine up too. I couldn't disconnect from intercom and thus couldn't connect back to my Zumo's mp3 player. So both of us would have to re-boot the G4. So when I called tech support about the issue, their answer was that we were not using the units exactly like the manual says so they are not responsible for how the units react. Nice answer. No offer to forward the issue to R&D to review.
Battery does seem to last very long. Great capacity. But not sure about longevity. No replacement available from Scala at all. I used mine in rain for 3 days. No problems.
If you read reviews on the internet, you'll see they are not very positive. I made the mistake of thinking they'd fix their problems in future upgrades. 2 revisions later and still have a few re-boots a day. It seems to me there are much better choices out there.