I haven't used Avaya Red for a few years (but I still get called for advice) and it was a great product for Contact Centres with bullet proof reliability. Was never a great fan of the Nortel stuff though.
In the middle of the roll out of CUCM and not impressed, in some ways our retiring ISDX is better....
I haven't thought much of Lync either and unsure of Unify's direction post take-over. I've been doing telecoms long enough to know there is no perfect product out there and I also know it is a dying industry and look at other options.
This bankruptcy has been coming for a while due to the loans / credit coming to an end and needing renegotiating. It's not as final as a UK bankruptcy and several of the US airlines have been in and out of Chapter 11 over the years (I think they all the major ones filed for Chapter 11 after Sept 11).
The difference with Nortel is that they previously had to sell most of their assets after doing an Enron and surviving on credit which disappeared with the financial crisis.