I was approved for a complete infrastructure upgrade - domain servers, Exchange, switches and phone equipment - at the end of last year. I talked to several vendors for the phone system - the one I went with was the only one that confirmed that Mitel had clients using their product with Ex2k10 and had it running in the lab. While they (the vendor) had no experience, they promised to work with me to make it happen so I've been lucky so far. Good company to date - no problems, they've been very prompt to work with and have researched darn near as much as I have, if not more so. My impression is that they like the idea of getting one of these implementations under their belt so that they can offer it as an option.