Actually the sound improvement is not that big a deal after the last firmware update sorted out the direct outputs. Good patch building will get you great tone out of the Vetta II without the need for the mod. I gave it some serious thought, but found that the sound comparisons were based on using the exact same patches (that were optimised for the modification). You could just as easily build a patch that would sound better on an unmodded Vetta because the patch would have been built for the unmodified version.
Having the real amp names is a cool feature, but if that's the only benefit and there's the risk of bricking the amp, I decided against it. It's entirely up to you, but I got years of awesome use out of my Vetta II combo without the Armin mod. I'm now using DT25 and DT50 amps, so I'm not using the Vetta II anymore.