One issue that I consistently had with it (before disabling it entirely since it lags me out) was the volume. I had to manually set every teammate's volume much higher than default in order to hear them. Everything worked fine, but the default volume was way too low.
I have one weird experience with STO: It doesn't register when I plug in my (USB) headsets after I started the game. I have to restart the game. Since I don't usually have the headset on, this is quite annoying.
I have the same issue with a standard 3.5mm jack. I have to make sure my headset is plugged in before I start the game or the sound will keep coming out of my speakers instead.
All of these issues you guys are describing are normal baggage when dealing with audio pipelines.
USB audio devices will not register on an application with a fixed audio state, you need to plug it in before you start the application you wish. This is a problem with most applications on Windows.
This can also affect Sound Cards with 3.5mm 'smart jacks', because it treats them as customizable endpoints, so it acts like USB; many of the newer Realtek and VIA integrated cards do this.
If your volumes are too low, make sure to adjust your windows volume up, and if that doesn't work. There are master volume levels in the voice chat options, you do not have to raise each and every person individually if everyone is quiet.
You can also raise your mic levels if they hear you too quiet.
The talk key is mappable like any other key in game via the ground and space key maps in options menu.
In the voice chat section you can also switch to 'open mic' so you don't have to deal with it anymore.
If you're having lag issues it is probably a case that you have a lack of available bandwidth or high ping already and Vivox simply added to your problem, we have the same issue with some of our new broadcasters on Trek Radio when they first join and try to do their shows ingame.
Before you disable STO's voice chat, run a traceroute 'tracert' in the command prompt to both Cryptic and Vivox's servers, which addresses currently escape me but tech support should be able to get you and see if you're getting a node lagging somewhere along the line, if there is. You'll need to call your ISP (or whomever owns the node) to get the problem resolved (make sure to give them the address for the laggy node).
Most broadband connections should be able to support both STO and Vivox with plenty room left over for tuning in to trek radio :p, if you're not able to do that then you're not getting what you're paying for
In the rare case that your connection is actually rated so slow that you genuinely can't sustain both Vivox and STO then you'll have to unfortunately disable it; however this situation is much rarer than it used to be in developed countries.
THESE ARE NOT OFFICIAL SPECS, just my take on it...
MINIMUM for Connection:
1.5 Mbit Download
1 Mbit Upload
Ping < 250-300 ms
Recommend for Connection:
4+ Mbit Download
2+ Mbit Upload
Ping < 150-200 ms
What I Have:
18+ Mbit Download
4+ Mbit Upload
Ping < 100 ms
I hope that helps you guys and please check out my show at 10PM EST
SHAMELESS PLUG FTW!
PS: Hopefully a dev will take this info and make a FAQ because the Vivox feature really needs a more comprehensive tutorial that includes proper configuration and technology limitations.