I've had the HP t5720 for some days now, and I've got it running everything that I need. Some notes:

1. If you get this, make sure you install the latest OS and BIOS (available from HP).

2. You have to edit group policies using GPEDIT.MSC in order to unlock a number of features.

3. By changing the environment variables to point TEMP and TMP to a network drive, and installing programs to the network drive, you can install huge numbers of programs without running up against the internal flash drive limitation (512 meg on mine). I'm posting from the thin client now using FireFox 3.0.

4. I've tried installing full XP using flash drives and USB drives. Unfortunately, I haven't succeeded (the install will work, but the thin client bluescreens). I know it is possible because other people have done it but, since it's doing everything I need with XPe SP2, I probably won't bother trying.

5. The only software/hardware that was problematic was MagicJack. After much experimentation and research, it appears the problem is due to the latest firmware in the MagicJack. By downgrading it to an earlier version and blocking automatic upgrades by editing the HOSTS file, it is now working reliably.

6. I previously reported (I think) that the thin client has a gigabit NIC. It does not. However, there is an inexpensive option that adds a single PCI slot. I've ordered it and will use it to install a gigabit NIC.

7. It has the Sygate firewall installed as part of the OS. This is both good and bad, as ANY program that accesses the LAN or WAN must be expressly entered into the Advanced Rules. Moreover, it was necessary to open the firewall to every address on the LAN. However, because writes to the internal drives must be manually committed by the flash management software, the odds of anyone getting past my hardware firewalls and doing any damage are negligible -- even if they do, a re-boot will fix everything.

8. I wouldn't recommend getting one of these unless you are reasonably comfortable with how computer hardware and software works. This is not an "out of the box" project. It does take a fair bit of tinkering if you want to have it running a lot of software and hardware.

Conclusion: This has been a fun and interesting project. I've now got a $150 thin client running my FTP server, MagicJack, my VNC server and a variety of other software. It's power consumption is a fraction of a real computer, it re-boots virtually instantly and, of course, is on all the time. This makes it very practical for use as an always-on home computer -- it makes a great internet appliance, LAN monitor, etc.

If you get one and want any details, drop me a PM.