I have tried it on my X31 and it works well. I bought the adapter via eBay, but I'm pretty sure it is from the same seller. I bought it from
microsatacables.
I first used it briefly with a 3 year old Samsung SSD. I am now running it with a Crucial C300 64GB 1.8" drive. You really need the 1.8" drives which are all micro-SATA so that you can fit both the drive and the adapter in the bay. There is plenty of room for both. I added a little bit of foam to keep the drive from flopping around in the bay and I am not using the caddy that the original PATA mechanical drive used.
Here's a quick performance comparison.
The Samsung drive worked without a hitch, but the C300 wouldn't format correctly when using the Windows 7 installer. I created the partition with the Windows 7 installer and then formatted it with a XP install disk and finally finished the Windows 7 install.
Performance is quite good on these old laptops with a SSD and 2GB of RAM in Windows 7. It easily bests a netbook and is probably on par with one of the newer (and expensive) Core Solo 1.3GHz ULV CPUs. The battery life on my X31 probably won't match one of the expensive ultra light notebooks, but I paid a lot less.
There's another thread in the T4x section that gave me the idea.
SATA SSDs generally perform better, are cheaper, and you'll be able to use the SATA SSD in a future laptop.
You might need another adapter though.