The main reason I went for MR816 was because I use Cubase, so the extra tight integration was alluring - and it is nice and working well.
Also you seem to get more for less with MR816...just not multiclient operation [:(]
I had the opportunity to do a comparison btw. FW-800 and MR816 - and well not much difference in sound quality of the Mics, maybe the MR816 was a little bit more crisp. Both where stable, but I could get the RME all the way down to 64 samples w/o drop-outs, the MR816 started with dropouts at 96 samples.
I must admit that I sort of assumed that since the MR816 is supposed to be a professional audio interface, it would naturally have this feature, and I think its shame on Steinberg for not having provided this.
I hope MIR Pro will be released some time soon, preferably by august first [A] - and yeah you're right it would be great to have VI proxies in your sequencer.