Hi!
To get some interest going for the combo IRay+SI, I figured it might be a good idea to start this thread along with some info on how to get started and a place to collect community test renders&tips.

...so without further ado...

To get started...

• Installl ctrl_ghost_settings from here (IRay is currently unsupported officially, needs this plugin to be activated)
• Get Primitive->Geometry Shader Primitive
• Open its render tree
• Connect a ctrl_ghost_settings node to the Geometry Shader, open properties
• In the "Progessive Rendering" tab, select IRay and set values at bottom to something like 2000/20000/120/0,001.. still figuring out what works best here

Some of the "selling points" of IRay:

• comes free with every Softimage
• pretty fast
• progressive, means you can test really well, seeing result right away
• emissive materials
• IBL for free
• very fast depth of field effects
• bump, displacement
• good integration .. Render Region works

Some drawbacks...

• no hair, subsurface scattering
• only GPU rendering, CPU not utilized (there seems to be a hybrid mode, but have no idea how to activate that)
• limited by GPU RAM. You won't get very far with displacement/large scenes and a 768MB gfx card
• no motion blur, bokeh type dof
• no render tree nodes (mixers,lookup etc.).. Everything needs to be done with textures
• no volumetric rendering
• no instancing (?)
• only mia_material possible as material

...And some tips:

• Install something like Real Temp GT to monitor your gfx hw temps. GPU rendering could overheat the card if it isn't properly configured.
• only mia_material works (not even Architectural -- even though they're the same internally)
• For IBL, just setup a Pass environment
• for textures, use a Projection_Lookup node plugged into a mib_texture_lookup node (results in error, which can be ignored)
• for bump maps, use a Projection_Lookup node plugged into a mib_bump_map node (plugged into mia_material's bump port)
• for specular like reflections, use a low refl_gloss value of about 0.2
• for DOF, use physical_lens_dof in pass or camera, bokeh shaders won't work
• Max Timevalue in ctrl_ghost_settings is the maximum render time in seconds. Quality seems to be controlled mostly by this.

Please post all your results here!
and let me know if I missed something in this short intro

Here's my first test, emissive textures using mia_material's additional_color slot, render time was 5 minutes on a GTX 460.

another test using additional_color and dof
(10 minutes rendertime/gtx460/768mb)

Testing max polycount with a zbrush model... around 1.2 million quads seems what at most goes into the 768MB of my gfx card .. so a 3GB card would hold around 5 million polygons

It looks really interesting. What's needed to run IRay?

It works with any modern graphics card and newer softimage releases. Nothing else is required.

My graphic card is a GeForce GT 555M, should it works with this card too?

Not sure, you'd have to try by installing the plugin &setting the options mentioned above&opening a render region.

Oh yes, definitely. I was asking only because I already tried and it didn't work. I was wondering if it was because of the video card.
I'll give it another try though, I could just have done something wrong.
Thanks rray.

If you see 'no cuda devices found' in the error log, that means your graphics card isn't supported. I've had some trouble running cuda on a mobile card even though it officially supported cuda.

Very interesting topic, thanks
I have tested iray displacement and seems like that it doesn't use power of gpu because both most of my RAM and cpu usage were about 100% at the preprocessing and I got valid displacement with some custom nodes like aa_Ocean displ\BA_fractal.
Also a good news that we can use partially every light shader on the lights with a prefix "mia\mib"
And thanks for the bump tip, earlier I could not get the any result with this