From my testing 600 took about 15ms. 100k would take about 2.5 seconds.

For me 600 iterations takes about 3ms (I guess my laptop is a bit faster). A decent range to shoot for is .5-1 sec.

Test program:

    crypto = require 'crypto'

    password = 'testing'
    len = 128
    salt = crypto.randomBytes(len)

    iters = Number(process.argv[2] || 600)

    console.log 'Testing iters=%s', iters
    for i in [1..10]
      start = Date.now()
      crypto.pbkdf2Sync password, salt, iters, len
      elapsed = Date.now() - start
      console.log '   Test #%s - %s ms', i, elapsed

Output:

      $ coffee pbkdf2-test.coffee 100000
      Testing iters=100000
         Test #1 - 497 ms
         Test #2 - 510 ms
         Test #3 - 496 ms
         Test #4 - 525 ms
         Test #5 - 510 ms
         Test #6 - 493 ms
         Test #7 - 521 ms
         Test #8 - 518 ms
         Test #9 - 510 ms
         Test #10 - 498 ms

      $ coffee pbkdf2-test.coffee 10000
      Testing iters=10000
         Test #1 - 54 ms
         Test #2 - 50 ms
         Test #3 - 50 ms
         Test #4 - 55 ms
         Test #5 - 51 ms
         Test #6 - 52 ms
         Test #7 - 50 ms
         Test #8 - 49 ms
         Test #9 - 51 ms
         Test #10 - 50 ms

      $ coffee pbkdf2-test.coffee 600
      Testing iters=600
         Test #1 - 3 ms
         Test #2 - 3 ms
         Test #3 - 3 ms
         Test #4 - 3 ms
         Test #5 - 3 ms
         Test #6 - 4 ms
         Test #7 - 3 ms
         Test #8 - 4 ms
         Test #9 - 3 ms
         Test #10 - 3 ms

Nice, I was actually testing on my server hardware which is obviously lower end. This is hopefully useful for people though.

For me 1 second seems pretty aggressive, that's CPU time/latency per login.