I recently upgraded to Vegas Video 3.0. I use it for audio only. What's the benefit of upgrading to 4.0?

With the input monitoring feature will the software switch from playback to input when you punch in? Can't figure out how to do this in 3.0. Doesn't seem posible.

I am getting a UAD-1 card. Mackie says it works well in DX with Vegas 4.0.
Does that mean it's not happening with 3.0?

Also I see a lot of postings complaining about bugs in 4.0 that weren't there in 3.0.

Any comments about that?