I had to post some of my tests and findings, Via Cider and Oblivion as well as managing to get HDR running on Oblivion! I know there is allot to read and I dunno what results other will get, Like I stated Below I am running the 2.4 Ghz Dual Pentium using the Radeon HD2600(256 Vram) and 2 Gigs of Ram. Am not familiar on what other Cider Programs will do, I used this Method on Puzzle Quest.app...
Hey I managed to get Oblivion HDR working as well, after fidling with the Ini Files and Fiddling with the Config Files in the Cider Program... Simply put, go into the config files in Preferences in your Cider program, Scroll down to GL extension and put 'Y' on it...(Open the config File using Text Edit)
So my Configs look Like this
[d3dgl]
"AnisotropicTextureFiltering" = "Y"
"VertexShaders" = "Y"
"PixelShaders" = "Y"
"PixelShadersLevel" = "2.1"
"ClipSpaceFix" = "Y"
"FragmentOffset" = "Auto"
"FixedProgram" = "Y"
"RectangleTextures" = "Auto"
"DynamicVBO" = "Y"
"IndexVBO" = "Y"
"FBO" = "Y"
"GLSL" = "M"
"VertexShadersLevel" = "2.1"
"FloatTextures" = "Y"
"OcclusionQueries" = "Y"
"fbobackbuffer" = "0"
[opengl]
"FixedGLExtensionBuffer" = "Y"
"GLExtensionBuffer" = "4096"
(I also Got VertexShader and Pixel Shader converted from 2.0 to 2.1 (aka Pixel Shader 3.0 for folks that don't understand the lingo) Simply type in the quotations 2.1
Am using the Cider program from Puzzle Quest so its a fairly recent Build.....
My ini looks like this for the Multi Thread Users... Did allot of research and it works, my system spec is the 2.4 Dual Pentium with the 2600hd Radeon and 2 Gigs of ram...
First off Yer ini Pref is located in Main hd/User/owner(aka the main user of the Mac)/Documents/My Games/Oblivion... You Open the ini File Using Text Edit...
Memory Tweaks:
uInterior Cell Buffer=3
uExterior Cell Buffer=36
The above values determine how many cells (whether for interior or exterior areas) are buffered into RAM. Note that usually the value of the Exterior Cell Buffer variable is automatically set by the engine based on the size of the uGridstoLoad variable. The higher that variable is, the higher the engine will raise this value. However if you want to smooth out your FPS, try manually setting a higher value for both of these, depending on how much RAM you have. For 1GB I recommend doubling the values (6 and 72 respectively). For 2GB of RAM, I use 16 and 102 respectively. For higher amounts of RAM, try raising them higher, however note that you should also raise the iPreloadSizeLimit value below.
iPreloadSizeLimit=26214400 - This setting appears to determine the maximum amount (in bytes) of RAM allowed for preloading game data. The higher the value, the more chance you have of reducing stuttering. The default value equates to around 25MB (divide the setting by 1024 to get KB, then by 1024 again to get MB). For those with 1GB of system RAM, try doubling the variable to 52428800. For those with 2GB, try double again at 104857600 (100MB). You can raise these values even further to experiment, however note that raising this to a large amount doesn't force all the game data to sit in RAM, and can actually cause crashes. I suggest the maximum anyone should set this to should be around 262144000 (250MB), even for 2GB of RAM. Make sure to raise your Cell Buffer values accordingly (see above).
Multithreading Tweaks:
bUseThreadedBlood=1
bUseThreadedMorpher=1
bUseThreadedTempEffects=1
bUseThreadedParticleSystem=1
bUseMultiThreadedTrees=1
bUseMultiThreadedFaceGen=1
iNumHavokThreads=5
iThreads=9
iOpenMPLevel=10
Also to Force the 3.0 Shader
bAllow30Shaders=1
(simply use the find fuction in Text Edit to locate all of the thigs needing to be tweaked

)
Next in the same folder to where your ini folder is at is called Renderinfo.txt
Get the Shader packet info which if yer using the set up I am the standard iMac setup the packet will be 2...
Now go into the Ciderized Oblivion Data file Scroll down to folder Called Shaders, Rename shaderpackage002.sdp to something else, I jes added a letter to mine so it looks like this shaderpackage002a.sdp, Now if yer using the same setup system that I am then For Bloom based Game use Shader packet 8, (jes Duplicate it and rename it shaderpackage002.sdp) and if You want to try out the HD Format Duplicate Shader 10 and rename it shaderpackage002.sdp... Do not delete Your renamed shaderpackage002.sdp, for back up purposes. If you have Shader Packet 8 Active HD wont work and if You have Shader 10 active Bloom wont work so it all varies on taste.
Experiment a little, I am running Oblivion on Full everything, Plus OOO and MMM as well as all the Trimming Addons working. I am still trying to Fig a way to fix sound, but doesn't seem to figure out anything else atm... I am still getting random Crash's, but I believe that might be because of the massive addons I am running on it, but I don't know yet.
I dunno if posting here was of any use, I hope it helps ^^ If any Ideas on how to fix the sound send my way. Jewel Quest uses the 1560 Cider Build, Side note Don't Forget to get yer hands on Direct X Program to install in System32 .. I got my hands on d3dx9_24 on to d3dx9_34 all installed in the directory... Hell I even got D3dx10_33 and 34 installed, (Its usless atm but might come in handy for future releases of Cider

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Allot to say, lol I had to post my findings Hope it helps!
Still working on the sound Bug, seeing if the actual Cider Program is the sole issue of the sound... Or if anyone has a newer Cider working with Oblivion that doesn't have the snd issue I would love te get it and be able to disect it...
Update: I wanted to see what happens if I went further then 2.1 on the Shader configs in the Config CIder file, I did 3.0 and it seems to run faster... Does anyone have an understanding to why?