It seems to be pot luck really.
I re-lamped eight external swan neck fittings on a pub with CFLs around three years ago.
They were all done at the same time, using the same lamps bought from the same place.
Whilst some of the fittings have been re-lamped twice since then, two of the fittings are still running on their original lamps.
How odd.
Not as odd as you might think - when a maker claims a lamp has a life of X'000 hours what he means is that by X'000 hours 50% of the lamps will have failed.
I've got CFLs in various places in the house - can't say how long they've been running, but some have been in for a number of years and are still going. I've not had any fail yet. I actually like the 10-15s ramp-up to full brightness...
Got 3 outside, and the light from them is fine.
I wonder if orientation affects life? Mine are all installed either horizontally or base-down...
I've also got some electrodeless induction lamps, and apart from one catastrophic failure I've been very pleased with them indeed - they work extremely well, and I shall be sorry to see them go - great technology but GE never got round to making anything other than an RO80 lamp. However there have been a few other packages launched by other manufacturers recently, so who knows?
LEDs? I too have tried GU10 ones, and they were truly awful - horrible cold colour and useless at lighting up a room. But they will get a lot brighter - commercially you can now get LED street lighting, and the lamps go up to well over 100W, so I imagine they're pretty bright, and if the makers expect them to be a success they must have a decent spread too. The technology will trickle down - it always does. How many years ago, for example, would people have thought you were mad to say we'd soon have metal halide lights in our homes and our cars?
I'd like to try some dimmable fluorescents, and I would really like to re-find a new lamp type I chanced upon on a website a couple of months ago which was a flat panel, 10's of cm square and very thin, but I can't remember who made it or what technology it was.