I'm one of the ones who's raved about the Intensity vest (also the larger Synergy). There have been some durability issues with the bladders and parts, but so far Nathan and/or Hydrapak have been very responsive. This is actually a small ding - the latest part that broke was an elbow connector and I really considered it normal wear and tear. I'd have been much happier to buy a new one for $5 or $10 rather than try to rely on the warranty department, but they didn't have them for sale.

Another question I have is that they've redesigned their 2 liter bladders with a hard slider across the top. I can't imagine this would be comfortable on most women's narrower shoulderblades. That's a speculation and not an experience, but you might check which bladder the new Intensity packs are shipping with and search other forums for people's experiences with the newer bladders.