I didn't like it. I actually thought the points about a group of friends aging were extremely well done. Sure it was sad to see, but that's a part of life, which is something this show has done so well. Even though I may not have liked parts of the episode, I thought it maintained the show's adherence to the truth of being alive.
But that said, I feel like the death of the mother cheapens the show. From the finale, I didn't get the impression that either Robin or Tracy were the one true love of Ted's life, which kind of renders the entire show pointless. The whole point of Tracy was to show Ted that Robin wasn't the person for him and that there was someone out there that was better than who he considered the perfect woman. And the dialog at the end from the kids made it seem like the relationship between Ted and Tracy wasn't as special as it was made to be throughout the show. In a way, it retroactively makes the entire story a ploy as to get his kids to come around to him dating Aunt Robin.
I think the cognitive dissonance is what really gets to me. What is this episode (and by extent this series) trying to say? We spend 9 years explaining why the relationship with the mother is the epic love story worth waiting for, but here we're left with the mother dead and triumphant music as he brings Robin the Blue French horn. I could handle a sad ending, I could handle a happy ending, but I'm truly at a loss over how I'm supposed to feel.
There was a time where I wanted Ted and Robin to end up together and I couldn't believe there was someone out there better... unfortunately a big part of me wishes the show ended there...
Ultimately, I feel like the show outgrew it's ending and it's unfortunate that they maintained dogmatic adherence to an ending that no longer fir the story they were telling.