Well I've just watched the final two episodes and I'm...happy? I wasn't initially, disappointed and pissed off even. The 9th episode was sad yet made sense but in true Wilfred style the 10th and final episode was confusion after confusion. Questions were answered and some really interesting and unexpected twists on the story were thrown out - but the episode ended with me not feeling like I understood what had gone on.
But after reading reviews online and people's explanations I get it. And it makes sense. And it works. And I'm happy it's ended this way.
A truly amazing show from start to finish

if you need to finish it, finish it! And if you've never started it...start it.
Oh...and they ended by doing a couple of things I always hoped they would. So that's even better.