Hi Shim,
I am the creator of the vArranger software. Many musicians are giging with this solution today (me included).
I think that if you are giging, it is more secured to use a hardware sound module like Ketron SD2 connected to the computer.
vArranger can drive up to 3 sound modules.
Some users are using the SD2 for style playing (Ketron + Yamaha styles compatible (roland soon)), and some solo sounds.
And use some VST for Right hand melody like amazing PIANO sound...
When you use a mix of hardware and software synth, you will limit the risk.
vArranger offers an easy way to control features, like creating presets, changing sounds, triggering fills...
I am just back from 2 gigs I played with vArranger. It was very good with 0 problems noticed. After some minutes of playing, you forget that you are using a computer.
I just attached the pictures of the 2 gigs for you

I love to take my small package while I have to travel by air or train to gig.