I use these strings on my Fender Strat. I was looking for a kind of string which could give my a vintage tone. And that's what I found finally.
As I've put Pyramid on my Strat I noticed that the sound was way deeper than usual. It reminded my a lot of Hendrix. There's surely something special about these strings and I think I'm going to buy more. Anyway the things that immediately jumped to my ears are:
1) nice smooth sound, if you like 60s and early 70s rock.
2) They cut the mix more than I could imagine (and that's maybe the most important thing)
3) So easy to play (maybe too easy, I think I'll go for 10-46 next time)
4) Great sound if you play slide
Another good thing about these is sustain. And they also keep the tuning quite well. ANYWAY consider that you'll have to adjust intonation on your guitar a little bit. This, as far as I know, is due to the round core. We're talking about minor adjustments, nothing dramatic. Worth the price.
If you're looking for mellow strings, for creamy good old blues and vintage rock, this is the way to go.