I own the DG Stomp.
I think it's got good sounds compared to it's price. Much better than POD's.
I can get Vai'ish tone out of it, but I need also a DS-1 (which is ok).
My Vai preset:
Speaker sim. b42
DS-1 tone 1/2, drive 1/2 and level max.
As you can see I've tweaked the eq's very high. The DG Stomp is not made for very heavy sounds (more for nice bluesy ones), but this way I can nail also the Vai sound.
I like also Crunch1 with almost the same eq settings, and for the cleans Cl1 with treble at 10.
The compressor is not as good as it could be, but in this price range, it's ok.
I play an RG 570 /w Evolution bridge pu.