I've never used Empower, and I've never built a character with it (or seen it in a game I've played in). Now, I must admit that I don't play blasters in general, so I have no need of it.
I suppose if you never plan on draining, damaging, or using anything with a variable amount of anything, empower would fall off your list.
In terms of metamagic feats that I would take and use, the three I use most often are Invisible Spell, Sanctum Spell, and Sculpt Spell. I only use higher than +1 adjustments if I have some sort of metamagic cost reduction; that includes Quicken. Chain is better from a Rod because it's so limited. Honestly, other than the three above, I never use metamagic except in rod form.
If you ignore wealth by level, okay, a rod is the way to go.
An empower rod is 9000 gp. the WBL of 5th level wizard is... 9000 gp. At high levels, sure. Rods are the way to go. but you can only use one rod on a spell at a time. I'd prefer to spend my money on a quicken rod or maximize rod and empower it myself.
Now as for invisible, I can see this if you are doing the arcane spellsurge sorcerer thing. Arcane spellsurge is a 7th level spell. You'd use invisible spell at 5th level? Why? How many 1st thru 3rd level spells benefit from this feat in comparison to the wide selection of spells that empower benefits.
Sanctum? Useful for some weird spell cheese, but you usually can't take avantage of that cheese until higher level. I have yet to see a single spell that I'd use this feat on. (Although if someone has the Sanctum Spell Handbook, I'd love a link)
Maybe I need to redefine the parameters. You seem to be speaking about the feats from your own play style. I'm thinking of a metamagic feat that you would take at 1st to 5th level and can keep using as you progress in level up to 20th and never find yourself going, "Damn, this feat is taking up space." This is in comparison across all classes and playing styles. Yes, some feats are situationally superior to empower. Split Ray beats Empower when casting disintegrate. No question about it. If I was ranking feats, split ray is still in the top 5, but empower is still number one.
I saw one player go with only sudden feats, mind you. Admittedly, her spells weren't that impressive, but once a day, LOOK OUT, an Empowered, Maximized, Widened something smacking you upside the head.
Now, invisible spell, I've been working out weird things you can use this feat for. Create Trap turns nasty with invisible spell. I suppose if you are an illusionist/controller type, invisible spell would be up there, since one could start using it at 1st level.
But for a cleric, invisible spell would be next to useless. Druid, ditto. Across classes and across spellcasting types, empower has much more versatility then invisible, sanctum, or sculpt.
Now Sculpt, that has some punch. Burning Hands goes from 15' to 40'. I'll give you that.
But I think you are falling into the trap of assuming that higher level spells beat metamagic improved spells. Why cast Empowered fireball when Cone of Cold is better? Because at 9th level, Empowered Fireball kicks Cone of cold's ass. At 15th level, cone of cold is better, even if the damage is the same, because of the better save DC.
It's not just spell level... it's Spell Level, Caster Level, Saving Throws, To Hit, Spell Resistance, Spell Synergy, Feat Synergy, Spell Caster Class, and Spell Caster Party Role. Empower is more things to more people then Invisible or Sculpt ever could be. Also, I'm simply unimpressed with Sanctum. But if you have some Brilliant use for it I'm overlooking then please do share.
[Side note: I should add this to Handbook: The Spell Book. Speaking of, if you have a strong opinion about metamagic feats, feel free to download section SSII from my handbook then write up your opinions of why certain metamagic feats rock and other suck. I'm more then happy to include any and all opinions about the feats. I may list it as a Minority Opinion, because I've already scowered the internet and got most people's opinions and summed them up. But I promise to only change spelling, format, and grammar errors. The intent will remain as you write it. Just post your opinions in the Discussion area.]
Do note, if you have some sort of feat combo that is so overpowering that it wins every time, I will reconsider my position on Empower. I dunno, some invisible spell that lets you mind control a god or something. But it would have to be damn impressive to boot empower off the number one spot.
