If you run Mint/Ubuntu make sure you have the latest build as it supports the newest drivers. Also XMBC is working with the APU, you can consider that as well.
As for RAM, I would run at least 2GB with Linux or Windows 7. 4GB would be nice as you can then use 1GB for the video section. This is one of the little known facts about the Zacate. If you increase available RAM just a bit, it improves basic task and performance with media content.
The newest Silverlight 5 Beta I believe has Hardware Acceleration - http://www.silverlight.net/learn/vid...rlight-5-beta/
I can play 720p and 1080p test streams without issue with this driver on my AMD based laptop (Turon 1.9Ghz Dual Core, HD4200 IGP), I don't think the CPU part of the Zacate is that much weaker.
This should really only be a concern if you're a Netflix subscriber however.
As long as you have the latest Flash Player (10.2+) and latest AMD drivers, 1080p Flash streams will not be an issue.
Yes the Zacate is a bit more dependent on the GPU section for most media and visual intensive task, but is that any different than trying to do it on an Atom based board or on older hardware?
People fear not having enough power for new media formats and things of that nature.
Just think about what you want to do with a HTPC and consider what's happening. For me, I don't see anything happening that would effect video playback of current linear (over the air and subscription tv) content or all online content since the majority of it is flash. There is hysteria over 1080i since this issue was raised in a review of the ASRock board published by Anandtech. The true is, interlaced content is handled by the GPU just fine; If not your display likely does it anyway, most modern LCD's do this. This will not effect picture quality.
I am looking to build two systems based on this APU, a new low power HTPC to replace my 4 year old HTPC that basically idles playing content as everything I watch is off-loaded onto HD4670 video card. So why use more energy for this basic task than I need? I hardly use my current HTPC for more than watching TV and some console emulation.
The other system I want to build is a media server and it looks like the APU is up to the task of trancoding for streaming video. This system will be about twice the cost of the HTPC because mini-ITX server cases are a bit pricey and I wanted to use a bit more expensive Zacate board that has a PCIe 1x slot for a SSD Drive to use for WHS 2011 and either Twonky, TVersity or PlayOn.
Which motherboard I use for my HTPC will determine which case I use and ultimately how I go about getting Direct TV HD into my HTPC.