Hi Joshua, hopefully this is not too late...I use a VT4 system in our video setup, but it is not my main switcher.
As Kevin stated, if the system isn't configured correctly, latency WILL be an issue. We started on a VT3 and the PC I had built was either too much for the VT3 (weird statement I know) or VT3 wasn't that stable. I wasn't happy at all.
That being said, there's been drastic improvements in the VT4 system. We did a complete upgrade, and I would recommend it to anyone...unless you're going HD soon (this is a problem i'll face next year, unless newtek supports live HD). Many people in the VT4 community are helpful and willing to share tips and tricks to make it run flawlessly.
I use the VT4 as my IMAG switcher, providing an easy way to roll video files like our weekly video announcements, lower 3rds for song lyrics, scriptures, alert messages,etc. So basically, it is doing overlay/cg work. I depend on a hardware switcher to go to tape and do most of the switching. It was great to have that VT in place one Sunday though, when the main switcher died...all cameras are fed to both the main switcher and the VT for redundancy.
From time to time I will set up streams from the VT, which is very easy, but our streaming is mainly handled by streaming faith.
VT4 is a great production value, you just need to invest in the best components to ensure the system runs smoothly...the video drive configuration can get costly!
Our VT Setup (with VT4 I don't have any problems)
VT4.6; Dual 3.2Ghz Xeons; 2 Gigs Ram; SuperMicro Server Motherboard; 4 15k rpm 125gb Cheetahs for video; 80g 7200rpm System Drive for programs; 80g 7200rpm drive for media storage; RS-8 Switcher, SX-8 Breakout (I suggest getting the SX-84).
Oscar Matthews