I've just put a set of D'Addario's EPN115 - their pure nickel 11-48 set - on my strat. I got them as a freebie to try out (I chose them) because the order for my usual nickel wound 11s got delayed through not enough postage.
I must admit, I'm almost a convert immediately.
They feel smoother and sound smoother. Like Phil said about the SOBs, they actually feel kinder on my fingers (I've been playing various guitars nearly all day and the old finger tips were getting a bit "sore and tired", but this guitar's easy to play now...). But having said that, I know someone with a nickel allergy - he would hate these!
They're a bit quieter than nickel wound, and I was expecting this. At first I suspected that this might account for some of the smoothness in the sound, but no... I've just raised all the pups (ITs) by half a turn. I've got the volume back, but without the harshness I'd be getting with the pups that height for nickel wound. I might even experiment going higher.
The whole guitar sounds a bit fatter and warmer, but without loss of top-end. The biggest change is on the bridge pickup - WOOO! Switching to BKPs made the use of the bridge on its own more of a possibility for me, this takes it a whole new step.
I can see me having to adjust all my amp settings to take full advantage, but so far it's looking like my adjustments will amount to undoing some the some of the compromises I've been applying to get enough "oomph" without unpleasant "sting".
I'm not a complete convert yet - I want to see how they stand up to my playing and my acid sweat, and I want to spend time seeing what it does with all of the patches in my amp modeller, but so far - :D
I might well try the SOBs next - that's the direction I was originally going to go for a test of pure nickel before this freebie arrived. And if the SOBs last longer, then it's worth the extra. I'll see how these little beauties pan out first.
But Fernando, YES, try pure nickel...
EDIT: And I forgot to say - they're EXCELLENT for slide. This guitar's not particularly set-up for slide, and a strat can be a bit "fizzy" for slide anyway, but suddenly I sound like Ry Cooder!