Here's my full summary and review of TMNT #73 at TMNT Entity.
While the issue does sort of throw readers into the deep end and has some vital tie-ins (hope everyone got that FCBD special three months ago and is subscribed to Dimension X this month), this is a storyline I've been anticipating pretty hard. So I guess IDW's marketing team did their job. Especially impressive, since I'm not normally into the sci-fi and outer space adventure side of the TMNT.