I have. 120GB Kingston mSATA SSD and ZIF to mSATA adapter. It works but I had issues. Basically you had to reload the firmware after a day of usage or several turn on/turn offs. Not practical. Either the firmware itself did not like the setup or the SSD + adapter was not secured enough so that movement might have triggered a failure. But since copying music onto it was hit and miss I assume it wasn’t a technical problem. The SSD runs fine in my laptop.
I use a Toshiba MK1011GAH HDD now and the 100GB have already massively upgraded the life of my ZEN Vision:M. The real problem is the battery. It only lasts 4-5 hours. 3rd party batteries are a tricky fit. They’re not as thin as the originals.
My players runs daily since 2007. I love it and I carry it with me everywhere regardless of my phone.