Given the historically strong PowerPC support in T2 as a primary platform, expanding the support to also cover the Cell-based Playstation 3 from Sony was natural development - especially considering the effor Sony puts into promoting the Playstation 3 as "Open Systems" providing source-level Linux patches.
The Playstation 3 comes with an IBM / Hitachi PowerPC CPU combining a dual-core "Power" Processor Element (PPE) with "Synergistic Processing Elementes (SPE). Full-features Cell CPUs come with 8 of those SPE co-processors, while the ones in the PS3 come with just 7 of them "known good" (to compensate the yield during production) while a hypervisor shielding Linux from the real hardware take another one leaving 6 SPUs to program from within Linux.
The PS3 has only 256 MB system RAM, and 256 MB video RAM for the NVidia based RSX graphic processor. Initially the later could not be accessed from Linux thru the official Sony OtherOS andlimitted graphic applications to draw to an unaccelerated frame-buffer.
However either thru a security vulnerability before FW 2.10 or by using some form of OtherOS++ CFW full access to the RSX, and/or the seventh SPE and other system resources is possible.
Support for the OtherOS hypervisor firmware feature was officially dropped with firmware v3.21, on April the 1st, 2010 Either do not update, or hope George Hotz releases the custom firmware with the once advertised OtherOS feature restored, ...
Linux is not allowed to access the hardware directly, all I/O is passed to an hypervisor running on a SPU. Particularly no access to the NVidia RSX is possible, yet - limitting Linux and the applications to slowly blend pixels to an unaccelerated frame-buffer.
The "just" 256 MB system RAM are not exactly state of the art for an developer machine. On the other hand for an normal end-user workstations with just a browser, mail client, office application and video player it might be sufficient, though. With latest kernels most of the 256 MB graphic memory can be configured as super-fast swap space.
Some older PS3 firmware versions contained a bug, allowing to gain partial access to the RSX gfx chip, and thus 2D and Video hardware accelleration via the xf86-video-ps3 X.org video driver. This "security leak", however, was later fixed by Sony in newer firmware revisions.
Update: In latest years it also became possible to use certain vulnerabilities to run Linux as GameOS with full access rights to all the hardware, including the NVidia RSX. You find newer builds of T2 diretly installable in such a Custom FirmWare, e.g. at: https://www.youtube.com/watch?v=xrCppgWK3AQ.
The developer Tool DECR-1000 and DECR-1400 also have twice the precious RAM.