It’s a very good yoyo. I think you don’t see much praise for it because it’s older brother is the Draupnir and that is a very difficult legacy to live up to.
I have played four bi-metals, the YYJ Phenom, the Jazz-Yo Regulus, the CLYW Blizzard and the Valkyrie. The Valkyrie is the best performer out of all of them quite easily IMO with the Blizzard being the runner up. For a bi-metal it is on the heavier end at 65.6g and you can certainly feel it. It has a very solid and heavy feel at the end of the string. You can certainly play it fast but I’d say it is more suited to a slower speed. It spins for aeons and is very stable. Due to the long spin times and somewhat sharp rims it has quite the bite to it if you call it back early (and if it snags and hits your knuckles you are going to feel it). The cup it pretty decent for finger-spins and it handles horizontal quite well due to its shape. It has a pretty good surface for finger grinds though due to the rims it suffers with palm and arm grinds.
The engravings are beautiful but they do border on going a bit over the top I think. YYRs look very elegant so I think a bit less could have made it look even better. The green that I got mine in is great. It is a very rich green (think British racing green) that contrasts brilliantly with the rims and engravings.
Due to its slower pace and long spins, it is great for learning tricks and it is probably very good for 5a and 3a (I think it was used by a YYR team member for 3a at some big contest near when it was released). If you are looking for a light speed demon then I’d say look elsewhere though.