Before the current crop came out, I used a flash-drive in a LOW-performance bedside machine, because I could make it utterly silent and more kick-proof.
The technology I used (CF Card) is normally for cameras and VERY slow about mixed read/writes. WinXP boots to a desktop fairly fast, then staaallllls over a minute while it dinks around inside the Registry to setup and update the behind-the-scene stuff. Altho the Geode 500MHz is not a speedy CPU, I sense that the CF Card is often the real bottleneck.
The current SATA SSDs are optimized for winchester type read/write, and far faster than an old CF, so this isn't much help. Except to point out that "it depends what you do". Once I get the slug fully booted, it plays Solitaire slick as any other.
A side effect: because power is low and has no surges, this machine often rides through short power blips which reboot the main PC and the microwave.