As an economy traveller, I didn't realize how much international trips were if I used a lounge for hops. The CSR comes with free access to a large number of airport lounges, which was a benefit I was surprised I used.
So far, the Priority Pass card I got with my CSR has been completely useless. In San Francisco I was refused entry at the partner lounge because it was at capacity and Priority Pass holders are clearly the lowest concern; at the Reykjavik stopover there was no partner lounge at all; and in Paris the lounge was a 10 minute walk + 1 security checkpoint away from my gate.
I looked it up, and seems the lounge in SFO is the KLM/AF one. Which is weird because I've been in there at a "peak" time (I was on the daily KLM to AMS) and it didn't seem particularly crowded.
Though in general lounge benefits -- unless you're getting a dedicated lounge operated by the program giving you access -- are not something worth going for. Back when I had status on American Airlines, I and many other people learned how worthless the alliance-partner lounge benefits can be: in theory, as an AA Executive Platinum, I'd have access to a rather nice British Airways lounge when connecting to an AA transatlantic flight in Philadelphia, but BA's policy was basically "all times are peak times (so we can turn you away), if there's anyone in here it's at capacity (so we can turn you away), and if there's nobody in here we'll close (so we can turn you away)".
I looked at the Priority Pass offering and did sign up but it didn't seem very useful. I already have United Club (and, by extension, Star Alliance--which I've never had trouble getting access to) and Priority Pass doesn't really buy me anything.
Amex lounge benefits are now the same as Chase, both offer a Priority Pass Select, and now AFAIK offer the same number of guests. Amex also offers access to Amex Centurion lounges which are among the better domestic lounges.
You can still get into a Delta lounge as an Amex cardholder, but Delta has been tightening up its lounge access generally for a while. The biggest change was introducing two-tier membership; Amex cardholders, and even Delta's own top-level frequent flyers, now only get the base lounge membership (or equivalent). This shows up in things like being charged $29/person to bring guests with you, where previously you got two guests for free.
Honestly they're really only valuable if your home airport has a Centurion lounge. As much as I love Centurion lounges (and have access to them), I find myself in PP far more frequently.
Yeah, and if they're in the terminal you frequent too >.< At SFO, only T-I/T-3 (where the Centurion is) and T1-/T2 are connected airside. That said, I used to route everywhere via DFW so I could break the journey up and chill at the D17 lounge.