I've been using LabWindows/CVI now for most of my career, I remember when it first came out, and I used NI GPIB drivers from the very beginnings of NI. There's a history of CVI on this site somewhere.
NI's main product is LabView, I think CVI sells at about 25% of the rate for LabView, NI can tell us if they choose I'm sure.
A developer who can program in C is likely to use LabWindows, otherwise LabView. There are any number of almost endless threads on this forum for LabView Vs. LabWindows / CVI.
CVI is based on C, originally C89 and now with some support for C99. Several of us petitioned for C99 support and NI did respond. I've seen several of my requests implemented sooner or later in CVI.
And NI did implement 64 bit capabilities in CVI, so that's surely an indication of their intent to sustain the product.
It's not OO, so you can get weary of coding gobs of procedural code in C to get stuff done. Then again, you can use NI libraries with Visual Studio if you want to do an OO based application with the NI libraries.
Support's generally been good IMHO, with NI's response to questions / problems generally tied to how important the issue is perceived to be.
There is a learning curve, and sometimes the more you look under the hood with CVI sometimes the less impressed you become - but then, I've spent way more time with CVI than most users I suspect.
In general, CVI tries to insulate the developer from the underlying OS and its peculiarities, offering a way to get a lot done without becoming, for example, a Win32 expert.
So, you might find, for example, that the deployment tool built into CVI works, with certain peculiarities and limitations, but that you don't have all of the flexibility and features, of, say, a full InstallShield version. And the native CVI compiler isn't as fully featured as the latest commercial compilers, so you might wind up buying and using Visual Studio C++ or an Intel C++ compiler for release mode compiles.
It's all a compromise, cost Vs. features/capability. What are your other options, LabView? Same vendor. Visual Studio? No native libraries oriented to test/measurement/data analysis, and you're running managed code that might not do what you want when you want. GNU tools? Same issue with libraries. HP used to compete with HP Vee but I have heard nothing about that tool for ages, it may be dead. In fact, you could say NI sort of ate HP's lunch when it comes to test SW development - HP invented the GPIB, had the instruments, computers, operating systems, etc. from the 70's but NI largely has the test SW market today as far as I can tell, somebody correct me if I'm wrong.
