I just tried SD-Tools and got a "failed to read buffer" error. Then I noticed in the release notes that the author states that his program doesn't work with some Motorola devices and further more he says "Don't download". That sounds to me like the dev is not interested in fixing this issue.

If you have a Motorola device you can use SD Card Tester:
market://details/?id=air.SDCardTester

Before Optimization: (128kb was the default)
Write: 3.21 MB/s
Read: 9.7 MB/s

Cache set to 1024KB (1MB)
Write: 7.64 MB/s
Read: 12.05 MB/s

Cache set to 2048KB (2MB)
Write: 8.05 MB/s
Read: 11.73 MB/s

Cache set to 4096KB (4MB)
Write: 9.69 MB/s
Read: 30.64 MB/s

Cache set to 8192KB (8MB)
Write: 8.08 MB/s
Read: 11.75 MB/s