My experience of ATI matches the consensus over at www.avsforum.com - great cards crippled by sucky driver support. If nVidia had given their cards 10bit DACs and an electrically clean output, then the HTPC crowd would have probably dropped ATI in a heartbeat. nVidia has a reputation for producing timely drivers that support their hardware well whereas ATI drivers take an age to mature before they actually make good use of the HW.

Now if only ATI's hardware engineers and nVidia's software engineers would all jump ship and form their own company we'd be set.