The word is... bleh.
ATI still hasn't done it. From all indications, there are good things to come...and a lot of this may not really be completely ATI's fault (although they certainly are not blameless). ATI's chipset business has been the victim of terrible timing, bad (and soft) releases, vapor hardware, and multiple other issues...and buggy feature sets doesn't help.
It appears that all the south bridge issues from previous generations have been corrected with the SB600. It looks like a solid south bridge.
ATI has been creating some very powerful, feature packed, and cool-running north bridges.
A good south bridge and a good north bridge make a good motherboard, right? Well... in a lot of cases, yes. But in the case of ATI lately, the problem is in execution. ATI actually doesn’t manufacture anything. They are a company of engineers...they design things and own the patents, and contract out to fabrication houses to have the actual hardware (graphics chips and motherboard chips) built. Then, these chips which are fabricated at contracted plants are shipped to manufacturers who put them onto the actual video cards and motherboards.
Because of this situation (and Nvidia is in this exact same boat), ATI only has limited control over the products that actually end up on store shelves. They control the design of the chips, and actually do lay out a reference design for how the motherboard (or video card) should look and work. It's up to the manufacturers to actually execute the design and creates the products on a mass scale.
ATI's partners have been doing a pretty crappy job at this. Even some of the big names when it comes to motherboard manufacturers seem to have a hard time making a solid motherboard using ATI's chipsets (Asus is one example). I have no idea why...maybe they just don't put the same design resources and man hours behind ATI-based boards as they do Nvidia...because they figure the Nvidia ones are a solid name that will sell better. And they are right...it's kind of a self fulfilling prophesy...less man hours probably means less quality in the final product, which means nobody's going to buy it.
With all that said, the only thing ATI can do is keep on putting out better and better chipsets (and they seem to have a very solid set with the Xpress 3200/SB600), and hoping that the motherboard makers start turning out a wider selection and more solid products.
From what I've seen, ATI's reference motherboards (the sample designs they create to show the motherboard makers how it could work) seem to be very very good. For some reason, the motherboard makers seem to want to "improve" on ATI's reference designs...and so far they have failed to do that. In fact, in most cases all the production products perform worse and have fewer features than ATI's reference boards.
ATI has been suffering recently from just flat out bad timing of their new designs. They came up with the RD580 and SB600, by all accounts a very solid and feature-packed chipset (which also seems to be relatively cheap to produce and cool-running). By all accounts, a very nice product. The problem was that the RD580 north bridge was really designed for AM2...and they released it months before the first AM2 processors arrived on the scene. Because of this, the motherboard manufacturers were forced to make a decision...build a socket 939 version of the RD580 board to last a few months and then build another board with the same chipset to support AM2, or just wait for AM2 to launch and start working on RD580 then.
As you can probably guess, this is business we're talking about, and most manufacturers just decided to hold off making motherboards with the new ATI chipset until after AM2's launch. It seems that they didn't even start development of the boards, either...because here we are a couple of months AFTER the AM2 launch and the first Xpress 3200 motherboards for AM2 are just showing up.
MSI's K9A Platinum looks like a very solid board. I can't say for sure whether it has any little glitches or weirdness...it hasn't been out long enough for there to be a lot of reviews or consumers putting it through its paces.
The other currently available board is from ECS, and is not even worth considering. From what I've read the board is a mess with a very limited and unfinished BIOS...and its performance and features are nothing to write home about either.
DFI, Asus, and most likely every other motherboard manufacturer, all have Xpress 3200 boards on the way. They just STILL aren't here yet.
Also keep in mind that right now, Intel really has the performance lead (for CPUs) in most categories. Over the next month or two, we're going to start seeing ATI chipsets showing up on Intel Core 2 Duo motherboards as well...and they might even be a better choice (from an overall performance perspective).
ATI being bought by AMD is going to mean no more ATI motherboards for Intel...but that is long-term. In the short term, ATI may actually have the best chipset there will be for the Core 2...so it could be worth waiting for. Again, it all hinged on how the manufacturers execute the designs.
Sorry for the long post.