The new firmware really improves the performance of the Vertex 4 128 and causes a moderate improvement for the 256 GB version. Writing large files on the Vertex 128 GB now goes twice as fast, and 25 percent faster on the Vertex 4 256 GB. You will actually notice this increase when using the SSDs. In other areas the improvements are less drastic, which makes the average look less impressive.
If you own a Vertex 4 128 GB or 256 GB then we definitely recommend installing the new firmware. Do remember to make a back-up first, for example with Ghost, otherwise you will lose all your data.