1. How does the card stand on its own? Is it good, bad, or have potential? Is it worth being played?
On it's own, Jirachi isn't too great. His power to give him energy is nice, but since you can only de-evolve any one pokemon once, they will normally just be able to re-evolve when their turn starts (which could hurt you if they have a power that does something on the evolution). However, if you used Jirachi early on, you can stall people evolving to a stage 2, or really mess them up if they used a rare candy to evolve.
2. What popular metagame decks could it be used in?
Not sure about which ones are most popular, but it would be good in spread damage decks (Electivire TR, Mandibuzz BW, Metagross UL, etc.), as you could damage a stage 2, and then de-evolve them for the ko. Also works well with decks that can move energy around (Shaymin UL, Mismagius UL, etc.), as getting more energy on the field can save you an attachment. He will probably just be a tech that only works in very specific situations, but if those situations arise, he could completely change the game.
3. What combos can you use it with? How so?
As just stated, energy spread decks could lead to multiple kos, and de-evolving rare candied Stage 2s will really slow the opponent down. Trainer lock decks might even make it so that it is almost impossible to re-evolve a stage 2 that was rare candied before the lock got up, if the opponent runs little or no stage 1s
4. Give it a rating, and explain why you have given it that rating. You can also rate the card by rating the thread itself (out of 5 stars).
3/5. This is a middle of the road rating, because it really depends on your deck build. It will generally be a mid to late game card that can get energy back on the field, and possibly mess up your opponent with the de-evolutions. If you have a spread deck, and can move energy around from pokemon to pokemon, then this could be a very good card, and swing momentum in your favor. If your deck doesn't do any of that, then this card would probably be worthless to you.
5. How's the artwork?
I think this card looks pretty cool. I've never been one to care for artwork all that much, however. For me, it's more about what the card can do. That being said, it's not nearly as cool as some of the legends or full art cards, but still pretty cool looking in it's own right.