I can speak from experience that it is worth it. It won’t be a super speed demon, but it will make it somewhat more usable. I’ve done so with my Asus Eee PC 901 netbook which has the two PATA SSDs. Those SSDs are SUPER slow compared to the cheapest mSATA SSD you can find with more than double the space, and all you need is a MiniPCI-to-mSATA adapter (the Eee PC 901’s drive slots are MiniPCI). I documented all about it here: …wordpress.com/…/my-geeeky-experiment-part-3/
I’m running OpenBSD/i386 on mine which isn’t as fast as something like Linux, but it definitely felt faster even with OpenBSD after the hardware upgrade. I also increased the RAM to 2 GB which is the maximum amount supported.