When I was negotiating my salary with my previous employer the only thing I asked for was more vacation time. They refused and instead offered me an extra $3000 so I could take unpaid time off.
They ended up working me to the bone for 6 months then laid me off once the product shipped.
Little things like this can really give you insight into how a company works. If a company is only willing to negotiate on money then maybe money is the only thing they are interested in.
I'll play devil's advocate here: making special deals on benefits other than salary is a land mine. Everyone is used to the fact that people are paid differently, but people are used to uniform benefits (all you out there: please don't call out your exception to the rule... it really is generally a rule). It's likely to have a negative effect or morale, whereas giving you more salary won't. (Yes, people find out these things.)
This is the main reason I am a contractor -- I take a LOT of time off. For my clients, it is normal for contractors to have gaps in availability. For my on-site colleagues, they know that the vacation is unpaid.
Increasingly it feels that contracting is the most straight forward way to work for an organisation. They pay X, they get Y. No messing about with broken promises and vague commitments.
I've also been able to comfortably do contracts for companies that have worked friends (who are full time employees) to the bone. If they want a 60 hour week from me, they have to pay me 50% more.
Also, some contracting companies now give their long-time folks paid vacation. The "vacation" rate may not be as high as the "working" rate, but it still beats a blank.
They ended up working me to the bone for 6 months then laid me off once the product shipped.
Little things like this can really give you insight into how a company works. If a company is only willing to negotiate on money then maybe money is the only thing they are interested in.