To be honest, I wouldn't call the BlackMagic speed test app an excellent SSD benchmarking tool. It appears to have been designed for an era when video production/editing professionals were searching for the best spinning disks for video capture purposes and were not considering the need for booting and running the operating system and launching applications from the same disk.
Plus it has meters, but these don't cover the range of some of the fastest SATA-III and PCI SSDs now available.
For the purpose it appears to have been designed for, it does a decent job, but in a world were application performance demands high speed read/writes for small size random files (rather than running a sequential R/W test), it hardly seems worthwhile spending the time to download it.
The one advantage it does have over others, is that it is free and available in the app store, so it is simple to compare sequential R/W speeds with other users.
Xbench for OS X is quite old, but at least it supports 4K and 256K random read/write speed tests. However, you should be careful about comparing these results with SSD vendor published data or other benchmarking tools, as the queue depth and other factors might not match.
I'm not so familiar with the windows world, but from the SSD forums I'm using, it seems that AS SSD, CrystalDiskMark and ATTO Disk Benchmark are quite popular.
