As user of looongues years since the ancestor of the MX4 (the Mixpander 9 Soundscape brand bought meantime SSL), I hesitated to take this MX4 with MadiXtreme (which is actually the same card, the DSP less).
That is, for the moment, through a beautiful project studio at home ...
It is PC and Mac compatible but its routing software and DAW run only on PC, this is great, I'm on PC
PC: I7 Ivybridge, 16 gigabytes of RAM, SSD + external USB3 HD Audio for part ...
The drivers are super stable.
I regularly use the DAW that comes with it (but I think you still buy it, as I had before the card I do not know): Soundscape, which is also HYPER stable. Well, on the other hand, it only manages audio (not MIDI in this environment, just click and tempo in the last version 7).
Note the VERY VERY low latency, could be called "real time" so it is low
With Cubase or other StudioOne no problem either, not stall
It is sufficient to use the DAW "third party" to launch the "mixer" map and route I / O to I / O from your DAW (having choice to use this card in them).
No inconsistency, whether in XP or W7 ... Stable hyper in 2 cases.
I must try soon with PT 10/11 elsewhere ...
This card has two slots MADI, which makes a total of 128 channels manageable.
Latency of 4 samples ...
Supplied with plugs Equalizer SSL slice, slice compression SSL, SSL and compression bus. Moreover, in the mixer, it's fun, it offers you to open presets AWS900 => then opens a "mix" with the same virtual architecture that table, with plugs placed in the right places and routing is identical to the AWS900 There are other models of table SSL, I do not remember which too