"Tassadar" actually being a Xel'Naga mimicking him-- that's okay. So is the whole Kerrigan becoming Xel'Naga thing. Everything up through the final battle against Amon is somewhat contrived in that Special Blizzard Way, but I can live with it.
That final cinematic with Kerrigan (or "Kerrigan") showing up at Joeyray's and Raynor walking off with her…what. The. Hell. Guess there can't be an ending where Raynor learns to live with Kerrigan's sacrifice and move on. What this ending means is, I guess:
- Raynor's dead and is joining Kerrigan in the afterlife or whatever.
- Kerrigan is really dead, but Raynor's gone nuts and thinks Kerrigan's still alive.
- Kerrigan's alive (somehow) and no longer Xel'Naga (somehow), which makes her sacrifice seem less significant and takes a good deal of the punch out of the ending
…or…
- Kerrigan is really dead, but her spirit is still with Raynor. Basically, Kerrigan is Aeris; this is probably the best, or at least the most logical, interpretation that doesn't rob the rest of the endgame of its impact.
I never liked the whole love story angle of SC2 anyway, so whatever its meaning, that cinematic was pretty
ETA: Thought about the ending some more while in the shower. Rethinking things, there wasn't ever a guarantee that Kerrigan was going to die at the end, however the implication about her permanently becoming Xel'Naga was pretty strong. That said, two "Kerrigan is really dead" theories above could have "or Kerrigan is still Xel'Naga and/or in the Void" amended to them.
And yet, given that Xel'Naga clearly have (had?) the means to travel between the Void and Koprulu sector, a fifth theory:
- Kerrigan left the Void, lost her Xel'Naga powers (through the Keystone or a device like it), and went to Joeyray's from there. Maybe the DLC will flesh all this out

Still doesn't change the fact that this ending was MAD CHEESY.
Also, Xel'Naga look crazy freaky.