I can't state this strongly enough - MIDAS IS A SITUATIONAL ITEM!!!
It has quite a long payback time (i.e. before it's earned you more gold than you've spent on it), and basically commits you to playing a long game. This is great when you'll probably have time to make full use of it, but it's a terrible item when you need to be able to get involved earlier on in the game.
Look carefully at the situation and the teams before buying one - it can help lose you a game as easily as help you to win one!
One good thing about Midas is that you can always but the gloves of haste. If building a Midas is not worth it, getting an armlet or power treads became 500 gold easier.
It pays for itself in cost in bout 19 min the upside however is the increase in exp.
It is a godsend for a level dependent hero and makes you get really far ahead of others.
Dont underestimate the bonus AS.
Only downside i can think of is for a 2k item it doesnt really provide any survivability.
For example, I played a game yesterday, I was mid as Death Prophet, we had a Dark Seer, Nature's Prophet, Ursa and Earthshaker. We were against Tinker, Skeleton King, Phantom Lancer, Bounty Hunter and Kunkka.
It's pretty obvious to me that we had a lot more push, and they had too much carry - unfortunately Nature's Prophet went Hand of Midas and contributed nothing until very late - we took rax at about 30 mins, but the game went over an hour and we ended up getting massively outcarried. Really poor decision by him to focus farming over the other two options...
It's a good item but not really. It's situational. Some heroes make better use of another farming item (Bfury AM), others are better with an early aggression item (Riki, Spectre).
I also like it if I know someone likes to/is going build Necrobook. Like I know Blitz Spiritbreaker always builds necrobook so I get midas against that, or if there's a NP I check his game history for profit games and see if he builds it.
The gold is probably the least relevant part of the item -- the exp is what makes it.
Thanks for all the discussion guys, very informative!
Generally speaking, Midas can be a good item as long as you get it early enough. After the 12 minute mark you're better off just going onto your other items, but if you can get it quick (especially on attack-speed heavy heroes like Faceless Void), I say go for it. But I never buy a Hand of Midas after 12 minutes unless I'm really close to getting it.
8 minutes is my cut-off point. 5 and a half minutes is perfect farm. Anything after 8 is just too slow.
It's really good on any hero if you can get it early enough. Not saying you should just because you can, but if you somehow got 1900 gold in 5 minutes, even someone like Tide could make use of it, as it pays for wards every time it's off cooldown and can progress to him getting better items early on that can make a big impact.
I personally rarely ever get midas, not even on Prophet (I tend to rush a Medallion). If I do go Midas it's because I can tell I will have un-contested free-farm for a long time as a carry.
Also, about this:
The overall point I'm trying to make is that it should always be a situational choice once you've had a look at the team line ups and how the game is progress!
Again, you're completely right: even when you're playing with "experienced" players you sometimes see a guy rushing that Hand of Midas even though the enemy team has already destroyed 3 towers; then, they tell you HoM is core on that Hero. It happened to me more than once.
You can potentially get far more levels/farm from ganking and/or pushing than you can from Hand of Midas - although it does depend on team composition and opportunities.
The overall point I'm trying to make is that it should always be a situational choice once you've had a look at the team line ups and how the game is progress!