Today I setup my HP t5725 thin client to be used as my desktop computer at my office. What I did differently was to use an NFS mount for my /usr/, /var/lib/, and /var/cache/ directories. This allowed me to setup GNOME with only a 512MB flash drive inside.
It works well and is completely silent. I'm going to use this thin client to replace a laptop which has a loud fan (when it is on).
I was initially disappointed when I found that the HP t5727 uses around 20 watts of power, but considering the processing and graphics abilities, its not bad.
UPDATE: Its actually really impressive - this little thin client can power a widescreen 1280x1050 LCD display! :-)
UPDATE 2: After a few days of working with this machine, I'm really pleased. I'm also very happy with how an NFS filesystem works for some important parts of the OS. I'm using NFS for /usr and /var/cache.