I have heard of instability problems with sdr. It has been a while so maybe they have been addressed. Joe Ely here in town has the hdr and absolutely loves it.
I am wary of any alesis products even before they filed for bankrupcy and were taken over by the dj's (Numark). About three or four months before they were taken over I talked to one of the premier repair houses in Dallas. They had not been paid for warranty work for 6 months and could not get anyone on the phone to address the situation. They finally just started telling people that they were no longer taking warranty repairs until Alesis paid their tab. This, coupled with the fact that the older ADATs no longer had heads available (in my opinion making them obsolete by default eventually), just left a bad taste in my mouth. One man's opinion is another man's trash...
Just make sure they don't give you a free fog machine and strobe light with every unit sold...

Check out pyramix! Exceptionnal.
http://www.merging.com

Cheers
Benoit