I can see the need for the C natural key and even the F natural is handy on occasion, but what about the rest? They sure make the chanter look pretty, and complicated, but who uses them for what?
Mike
F : hardly ever, don’t like the sound, just pick the one F in Planxty Browne, which I don’t play seriously anyway
Gsharp: Fairy Queen (the hornpipe but not the same as The Queen of the Fairies and not the Carolan piece), when Sick is it tea you want and a few odd tunes
Bflat: Lady Aylmer, Valentia harbour
They look fancy though 
yes I agree Me
RORY
I think the extra keys can be useful for variation. One extreme of this variation which I am quite fond of is that like the Bothy Band does in a few of their recordings, starting of a set in D, G, or whatever else that can naturally be played on a D chanter and finishing the set in E or A major. Well, for me, this creates a BIG energy push in the music, and the keys would be necessary to do this. Anyhoo, that’s my 2cents.
-Mike
I have a fully-keyed chanter and, save for the Cnat, I haven’t learned to use them yet… 
A lot depends on the repertoire you play. I play about 90% Irish which means that I use the Cnat key from time to time and the Fnat occasionally. I’m getting into Scottish Lowlands music a bit so I’m beginning to use the G# key. I don’t have a Bb key and don’t know any tunes in which it is used. However, I know of a few people who play traditional instruments (Irish flutes, tin whistles, mandolins, etc) for different kinds of music and they argue that the more keys you have the more notes you can play and the more you can expand your non-traditional repertoire. If that interests you.
I’d have to say I play only Irish music on the pipes …well except for the odccassional renditition of Trumpton, Take 5, Take te A Train, Misty or some hackneyed heavy metal tune And I have to say that I encounter tunes that require keys all the time. I play sometimes with fiddlers and their fancy A tunes and the odd G minor tune.. more of which I’d like to learn… Thusly keys are good IMHonestO… and they look nice and complicated It’s all jewelry isn’t it? Chanter keys, car keys, cell phones, ampalang, regulators.
For your inconsideration,
Patio.
Florida Keys
mmm, key lime pie
My understanding is that the many extra keys came in with the gentlemen pipers of the 19th century, who played more than ITM on the pipes (and could afford it).
djm
I’ll take a Ki-------lo. 
Hey, hey we’re the Mon…keys…always Mon…key…in’ 'round
O-KEY Do-KEY, time to get back on topic.
Sorry. Since I contributed to getting off topic, I’ve found 4 of a number of threads on the subject of Keys to bring it back on topic -
http://chiffboard.mati.ca/viewtopic.php?t=12956
http://chiffboard.mati.ca/viewtopic.php?t=19250
http://chiffboard.mati.ca/viewtopic.php?t=20900
http://chiffboard.mati.ca/viewtopic.php?t=31153
Cheers,
DavidG
Good archivin’ mate! 
Breton tunes tend to use a lot of keys like B flat. To me, I’m interested in Celtic music with Irish music being predominate because of the instrument that I play. But I play welsh tunes, Scottish ones and occassionally Breton ones too. I just got back from Portugal who also have a big celtic music piping tradition similar to Galician pipes and those tunes sound well cool too!
Most pipers will definitely find that they’re fun to use in Slow Airs to add some character to them. Let’s face it, more keys equal convenience over cross fingering and more options to get creative with. They’re the equivalent of a Fish eye lens on a camera, used for dramatic and creative effect on occassion. I’ll soon have 4 keys on my up and coming chanter so will have lots of fun. I knew someone that had 5 keys once! I cannot remember what the 5th one was but it made good sense at the time of discussion at the session a few years back. I thought at that moment that his chanter looked great and with his playing ability, sounded great too.
I’m now wondering what that elusive 5th Key may have been?
Kind regards
Andy
The 5th key on my chanter is for d, an octave above back d.
Yep, the old flat sets often have a third-octave-d key. Arguably better in tune, depends on the chanter and reed.
You also see 2 more keys, the ‘Dsharp’ key (below the bottom E hole, usually) and the third octave e key (activated with the left index finger). A saw a pic of a chanter recently with 2 ‘short F’ keys, no idea why. I can however see a use for a long F and a short F.
F - the short and the long of it - the short, ring-type F key can be easier to access, and others on this board have previously expressed a preference for this. However, it can be a bit clumsy to hit if you are going to go from Fnat to E, or Fnat to G in a tune and want to hit the notes cleanly. Others on this board have previously expressed a preference for the long Fnat key. I find it generally more awkward to hit, but that’s just me. If money is no object, and you have both Fnat keys, you can take your pick of the two depending on where you are in any particular tune as to which Fnat key is easier for you to hit at any particular moment in any particular tune.
djm
just edited my previous post to insert the missing period ‘.’ .
What puzzled me is this set with two short Fs. Perhaps one was activated by the thumb? Just goes to show that there’s no end of experimentation that’s gone on.
Bill