Mother's Mercy is surely about The Mother, one of the seven gods, the merciful one. I think it will be about the Faith and the trials. Maybe there will be a teaser about Stoneheart, but I doubt it :/

That's what I was thinking as well and I'm guessing the episode will end with "For the Watch!"

Except unless Stannis magically teleports his way back to the Wall the decision to burn Shireen will not involve him, which is quite a big difference with respect to Stannis morals, ethics and state of mind. If it's purely Selyse and Mel who make the call the burn Shireen to help out Stannis then that changes the character dynamic completely, especially since in this episode it's Selyse who breaks down and ends up desperately wanting the burning to stop. It's not the burning of Shireen that's the problem it's the character assassination of Stannis that is the problem. People who never liked Stannis from the start are all fine and dandy with his total moral corruption. 

The show has become very lame in other story departments too, it lacks depth, subtlety  and complexity.

Having not read the books, I can't really understand the differences between them and the show. However, having read the Sword of Truth series, and seeing the horrific job that the 'Seeker of Truth' TV series did with the material, I can completely understand the feelings of anger. It's quite literally the same issue comic book fans have with virtually every comic inspired movie that's ever been made.

Really, there is nothing going on entire season. Only ep. 8 and 9 were good.
I just hope that season 6 will be last, coz it's starting to be a bit boring.

So very much this.  I'd say the same things about people who object to certain games, movies, books, comics etc...  Play/Do something else.

Never read the books and enjoying every episode.

Well, I don't know what's "boring" about this season. I read some complains because it's slow, when all GoT seasons were slow until the end. It's all about dialogue and a shocker resolution. Although I like more the previous season, this could be second in my rank. Episode 8 was outstanding, and today... I''ve never been more terrified seeing a TV show.

I've only skim-read the books and I think the show has improved a lot since a few seasons ago. The deviations from the books seem justified to me for pacing reasons.

Every time I think the show has an A+ episode I go on the internet and everyone's rated it as "C-, character X didn't stay true to their book character"

Personally i think this is one of the better series they've had of late.

In the past it's had what I called "The Walking Dead Syndrome".... episodes of nothing much happening, me thinking why bother it's boring, and then Bam - a great episode saves the day!!! But yeah I've really enjoyed this series, it's been much more entertaining.