Ask YC: Are you using O'Reilly's Safari Bookshelf?

Yes I use it.

Yes I recommend it.

It doesn't replace dead-tree in many cases, but for those "I need to know some obscure info or recipe for X RIGHT NOW" cases it's worth the $20 (IIRC) per month, even if I don't touch it for 3 months.

For books that I really want to read in-depth, I just buy the actual book. For bits and pieces augment-my-knowledge stuff, it's invaluable.

I have access to it through my employer, but very rarely remember that I have access to it. That said, I have found it useful in the past and would recommend it if an only if you'll remember you have it.