Has anyone zero'd the cells on an SSD?
SSDs degrade over time because the 'cells' they use to store memory can only be written to a certain number of times before they start degrading. As SSDs degrade, they start to become slower and eventually stop working all together (though the drive usually fails before all memory cells become non-functioning). 

To help slow down the rate at which SSDs degrade, many SSDs implement a technique called wear levelling, which requires a bit of additional memory management. In some SSDs, this can cause writes to become slower because it has to examine more memory blocks before it finds an unused are to write to (As mentioned here: http://www.anandtech.com/show/2738/8).

Thus, if the entire device is wiped (i.e. all bits are 'zeroed') and the data is rewritten to it, the memory will be rewritten in the order it went in and all clump near one are, meaning new writes should become faster again because there's now all the blank pages are grouped together and nothing needs to be overwritten.

At least, that's the theory. Now for the reality.

In reality all SSDs have different methods of reducing wear so this will only work for some. That article was written ~5-6 years ago, SSDs have changed a lot since then, they've become much better at reducing wear and employ different techniques.

Finally, remember that in clearing the entire SSD (i.e. writing a zero to every address) and then rewriting all its old data back onto it, you are performing quite a few writes to various cells. Depending on how your SSD actually works, this could improve write-speeds, but it could also not improve write speeds. One thing is guaranteed though, it'll wear down the SSD a bit and it will die a tiny bit faster. If you were to do this every week for the entire time you owned the SSD, you'd probably waste a fair chunk of its write limit just wiping it and writing data back to it.

Long story short: don't bother trying to screw around with tricks like this, just trust that the people with years of experience researching and designing SSDs know how to do wear levelling better than a bunch of self-proclaimed 'hackers'. Ultimately if your SSD write speeds are slow enough to be noticeably bad, you're better off buying a new SSD anyway.