Keys. Oh yeah. It’s astounding how many people like to play in F, Bb, and A. I tend to work around the lowest 2 semitones (clanky pewter and shoddy embouchure) so a 6-key seems perfect to me. Actually, a 7-key with a long Bb would rock, but I’m just dreaming.
My old 4-key kept me entertained for quite a while til I got a decent 8-key.
Cork, we need to clarify, here. Going for keys doesn’t necessarily mean going Boehm. My flute, a trad timber flute, is “keyed” but still simple-system; IOW the base diatonic scale is still unkeyed; the keys are for c, Bb, G#, Fnat (2 o’ dem puppies), Eb, C#, and Cnat. In this forum there’s a tendency to presuppose simple-system flutes, actually, whether keyed or unkeyed, as that specialty item of the Western flute world has been the thrust, here, from the start.
Not being a Boehm player, if I remember my hearsay correctly, Boehm fingerings have some real differences from keyed simple-system, and so a Boehm instructional wouldn’t be of much help except to a Boehm player. But your recommendations are helpful to those here who are, of course, and thanks.
But correct me if I’m mistaken. 
From an Irish Trad perspective you are correct.
Now if you want to play in Eb on a keyed “Irish” “D” flute these exersizes will give you a workout.
yes, you can play some really neat tunes with keys (Tom Mcelvogue’s compositions etc.) and the keys have saved my flute from jumping to its death from a table. I hate it when you have a suicidal flute…
Other than slight additional cost (which can be recovered on resale if you don’t like them), nominally extra weight, and slightly more maintenance is there any reason not to get keys?
I say get them if you want them.
they make finger twirls difficult…
'course that conical thing is no help either
do keep at least one Tipple
So who’s paying to get keys put on my Hamilton for me? Cuz I need them. 
I suppose it depends on what you call “slight”. $65 USD a pop isn’t unusual. Factor that by six, and…
The low C#/Cnat combo alone cost me $350, if memory serves.
Of course, those are Noy prices. Some may charge less. But I think it was worth it.
$65 a key would be a great deal! The makers I’ve talked to have been in the $100 plus range for each key…so that slight cost may be more significant than you think.
Eric
Okay, my bad. Just checked Noy’s site, and it’s $250 per key. That sounds right. “C foot with interlocking C, C#, separate $1,400”…I don’t recall that, but maybe the shock induced some amnesia on my part. I presume the Eb is assumed there. “Keys, low C, C#, each $500”…I presume that would be just one without the other, but I don’t see the point of it.
Might be his rates for the functioning C foot have gone up…it’s been 3 years since I first placed my order.
I’m guessing that the $65 figure I came up with comes from checking out pipemaker prices. For as expensive as sets are, the keywork can be mercifully inexpensive by comparison to flutes. $75 per key isn’t unusual as I recall.
Noy’s prices are comparatively high, but the quality’s high, too, and I only waited about a year. “Good, fast, cheap: pick two.”
Dominic Allan in the UK offers handmade pillar mounted keys for £110/E180 per key, or £800/E1320 for all eight keys fitted to a keyless flute. His keywork is great, and very ergonomic.
That is 3 keyless flutes for one fully keyed flute. But worth it I say.
~Hans
Looks about the same to key a Seery: 150 Euros per key, or $1185 USD for six. Oh, well, I guess I got that out of my system!! 
Hei hei
What began as a one-key flute eventually had more and more keys added to it.
In the process of adding keys, the diatonic simple system flute transformed into being a chromatic simple system flute.
The text, Exercices, was written for use with virtually any chromatic woodwind, including chromatic simple system flutes.
Actually, I like simple system flutes, in part because there is no faster flute on Earth!!
I’d like to see more makers offering keys of lower-cost materials, such as brass/nickle, as I need a flute, not playable jewelry.
silver is easier to work with
Cran seems to have a spare key or so 
Denny should have a good idea about that! The late Dave Williams, maker of pipes and flutes, used nickel silver for his keys and ferrules on at least some of his flutes, if not all. That stuff’s harder than stone.
I should have a lot of things…
Yep, four keys for my copley will cost more than the flute. So given the very high cost of keys, which ones do you want most?
I’m playing in a contra dance band and have been considering buying the minimum to make my copley fully chromatic (Eb, G#, Fnat, Bb). On other days, I think I might like to have that long C and long F, but not sure if it’s worth the extra $.
Jay
Given that the cost of six keys isn’t that much more than four keys, relative to the cost of a keyless flute, go for the whole hog. I can see just getting two or three keys, but once you’re up to four, it seems penny wise and pound foolish not to just bite the bullet and get six, especially if it’s a flute you plan to play for a long time (or a flute you might sell at some point for that matter.)
D to F transitions make the long F worth the money, and while it’s far from essential, the C key is nice to have for certain situations.
But “Whole Hog” wants 8 keys, not just 6. That’s why I’m looking for a less inexpensive alternative. One maker does nickle/brass keys, so that’s who’s getting my consideration.