Here is a post (#39) of David A. Hoatson, co-founder of Lynx Studio Technology on harmony-central.com :
Vista will work just fine if you are only using ASIO, since that bypasses everything Microsoft. If you do use the WDM driver (MME/DirectSound/Direct Kernel Streaming), then you are forced to use Microsoft components, and there are some new limitations with Vista.
The biggest problem at the moment revolves around sample rate support with Vista. Vista wants to be in complete control of the sample rate. That means that any application that used to set the sample rate by itself (CoolEdit Pro comes to mind), can no longer do so. The user must manually set the sample rate in the Audio Control Panel for the device in use. This also means that if you are clocking externally, as soon as the external sample rate changes you must also go into the Audio Control Panel and set the same rate there, otherwise you will not get audio. Some audio cards may get around this limitation with a driver rewrite (the code changes required are not easy), while others may decide that pro audio users really will just use ASIO and leave it at that.
Another issue has to do with device naming. Microsoft completely changed where the device names come from, and Vista the names of the devices by itself (with XP, the driver had complete control over how devices were named). This presents an interesting issue when dealing with a pro audio card that is also used for high-end home theater applications. To allow multi-channel playback for DVDs, the device must be named "Speakers" otherwise Vista simply won't present the Speaker Configuration to let the user select how many speakers they have. In a multi-card configuration, you end up with multiple devices all named "Speakers" which can be confusing to the user.
http://acapella.harmony-central.com/forums/showthread.php?t=1521198&page=2
Vista will work just fine if you are only using ASIO, since that bypasses everything Microsoft. If you do use the WDM driver (MME/DirectSound/Direct Kernel Streaming), then you are forced to use Microsoft components, and there are some new limitations with Vista.
The biggest problem at the moment revolves around sample rate support with Vista. Vista wants to be in complete control of the sample rate. That means that any application that used to set the sample rate by itself (CoolEdit Pro comes to mind), can no longer do so. The user must manually set the sample rate in the Audio Control Panel for the device in use. This also means that if you are clocking externally, as soon as the external sample rate changes you must also go into the Audio Control Panel and set the same rate there, otherwise you will not get audio. Some audio cards may get around this limitation with a driver rewrite (the code changes required are not easy), while others may decide that pro audio users really will just use ASIO and leave it at that.
Another issue has to do with device naming. Microsoft completely changed where the device names come from, and Vista the names of the devices by itself (with XP, the driver had complete control over how devices were named). This presents an interesting issue when dealing with a pro audio card that is also used for high-end home theater applications. To allow multi-channel playback for DVDs, the device must be named "Speakers" otherwise Vista simply won't present the Speaker Configuration to let the user select how many speakers they have. In a multi-card configuration, you end up with multiple devices all named "Speakers" which can be confusing to the user.
http://acapella.harmony-central.com/forums/showthread.php?t=1521198&page=2