I'm running a similar setup (but without an SSD) and also found some stuttering with HD content.
What I found to be the problem is that XBMC was not using DXVA hardware acceloration. Without the DXVA acceloration the Atom 330 is just not powerful enough to do perfect 720P or 1080P playback.
I've installed a nightly build a couple days ago and forced DXVA rendering. Unfortunately DXVA support is pretty poor at the moment in XBMC. Sometimes I find that using DXVA renders the lower part of the screen with a black bar. I'm still trying to figure out if there is a work-around. Hopefully a new nightly build will rectify this, but I'm not counting on it to happen soon.
If anybody has any suggestions and/or work-arounds it would be greatly appreciated.
Yea, i think you are correct, I am going to hope that some future builds improve the acceleration under windows.... though that said, I installed XMBC for windows first on my laptop just to mess around with it, and it plays everything perfectly (then again, it was like $1200 vs 3-400 for these ion builds), so i hope its not just a hardware limitation.
For the record, its only the larger BR rips that have been stuttering for me too, and further, I can play everything without a hiccup on XMBC Live with my setup, so it's something specifically with windows causing the problem.
Like I said, I'm just hoping that future builds of xbmc for windows will solve things and its not the windows framework itself putting limitation on the hardware that would prevent improvements in the future.
Hulu playback is pretty bad (though watchable) for me as well.
Though if someone is running this, or similiar setup under windows without flaw, i'm all ears for any tweaks or setups I could be missing, Thanks