OK, I recently bought a 20th Shiva with reverb and here are my impressions:
Firstly, engaging the reverb loads the amp down. You will hear it. It feels a bit softer, less punchy on the cleans. Can be compensated easily with the channel volume.
How does it sound? Alright, I guess. I can only use the knob a few hairs above zero, since the reverb comes on pretty quickly in overwhelming intensity (at least to my taste). Some people might find the higher settings more useful perhaps.
Why did I get the reverb option? Because I prefered the black tolex!
And I figured it wouldn't hurt having it onboard as bonus. After all, you can simply leave it disengaged.
Am I using it often? Not really. Sometimes on the cleans, but recently I have had it turned off. I use some delays in the loop, which itself sucks volume and tone, so using both reverb and the loop seems a bit too much.
I guess it all comes down to how much you need the reverb. Unfortunately, the Shiva's loop is subpar, in my opinion, so going with reverb/delay pedals is only a different route with similar results, if you know what I mean.
I remember reading that Reinhold Bogner once said that he felt no reverb was necessary on the Shiva and that it was only included because of people's demand. It is certainly true that the Shiva will sound best (and shine!) with as little in the signal path as possible.
Would I desperately want to get a Shiva with reverb again if mine was broken? Probably not.
Hope this helps. Have you actually played the Shiva + reverb? My comments naturally only refer to my own personal experience with this amp.
