The boxes are much more useful with root access.
I use one to run callweaver (asterisk fork), apache2, ssh, mysql, openvpn, samba, gcc, perl, etc.
Yes compiling is slow, but it has no problem hosting web pages, say, for an image gallery. For VPN, this device was not the bottleneck with my ISP.
The original PPC models were ~3X faster than the newer ARM9 variants computationally. Many operations were annoyingly slow (always waiting for aptitude to come up). However the ARM9 cpus, at 400mhz, are still better than some of the popular hacked embedded devices such as the NSLU.