That's pretty much what it is, a gamble.  It's all a matter of beginning/mid/late game and whether it's a rush map or not.  This question has been around since the beta, and it will never be answered.

Howdidudothat said it best, its a gamble.

I wouldn't think of it as a complete waste of time since there is allways a chance o unearth the +damage% or plus armor% or + antimater% artifacts.

Another thing about exploring is that you may come across planet bonuses while looking for artifacts.

If your advent, the research that makes it cheaper makes it far more worth your while. Add fully upgraded motherships colonization and you get free exploration.

Generally, I find myself not looking for artifacts unless I am playing a very large map and am going through a period of consolidation.  I did once find the phase accelerator (+50% pahse jump speed in-system) as the vasari, which made travel through pase stabilizers (with 2 leveles of phase tunneling) go ridiculously quickly.  One tactical defense fleet could defend the entire empire.  In early game or on a small map, the credits and resources needed for exploration would be much better invested into infrastructure or ships.  Let the computer (or your opponents) do the digging and annex the planet they find artifacts on .

As soon as someone finds an artifact, everyone gets a message saying "Another empire has discovered a powerful artifact at X." but will not say what artifact it is.

Searching for them is usually not worth it, but sometimes they can change the balance of the game if you've reached a stalemate with your opponents.

They are just there to add another level to the game. Not to say they arent useful, but in most MP games they arent worth the investment (personal opinion)

Against AI on al arge map, sometimes I indulge late game just out of curiosity.

Only a few artifacts are actually usefull

I wouldn't waste my money unless I have loads of it. You should spend your res on ships and structures.

Really, the only good reason to seriously hunt for artifacts is to go after the Archeologist achievement (find all 9 artifacts).

Admittedly, it was fun seeing a level 10 Kortul have a 200+ DPS from Pulse Beams alone with Power Surge (cooldown rate +75%), culture (+15% damage), research (+20% damage), and the Kinetic Intensifier artifact (+12% damage).

LOL...no, that is just the point.  It ISN'T FREE!  You pay to explore, which is why all the experienced players are calling it a crapshoot.  It is only free to Advent with research and a levelled up Progenitor, who we all say should do it.  Anyone else spending too much on exploration too early runs the risk of being killed by their neighbor who spends the money on military power.  Only in very long games with the AI can you afford this risk, because the AI is a lot easier to hold off than real people.

I suspect that most of the people posting in these threads only play against AI and not online multiplayer, which is kinda sad.