Hmmmm... I'm coming up with quite different numbers using Scala version 2.11.0-20130614-053437-70a93f52c3 (but I'm not sure that the difference isn't due to my inexpert use of Thyme):

```scala
scala> th.pbench { appendWithVector(nums) }
Benchmark (60 calls in 753.2 ms)
  Time:    6.338 ms   95% CI 5.991 ms - 6.686 ms   (n=19)
  Garbage: 3.650 ms   (n=15 sweeps measured)
res0: Seq[Int] = Vector(0, 1, 2...

scala> th.pbench { appendWithListBuffer(nums) }
Benchmark (60 calls in 317.2 ms)
  Time:    1.614 ms   95% CI 1.569 ms - 1.658 ms   (n=20)
  Garbage: 2.075 ms   (n=3 sweeps measured)
res1: Seq[Int] = List(0, 1, 2, 3...
```