Yes, it sets a plot for future episodes. Yes, it provides action and all the little things we love about Sherlock. And yes, it will keep watchers hooked on to it for the terribly short tri-episodic season.
Now that the basics are established let's break it down to the specifics (like Sherlock would).
1. The episode starts where it left off on the Christmas special. Anderson is still crazy. Lestrade is still in denial and Watson is just plain depressed and trying to 'move on'. Sherlock haters (or 'jealousers', if there's such a word) have united in memory of the detective. The build- up is perfect. The actors represent the viewers' reaction and unflinching patience over these two long years.
2. Watson's girlfriend and future wife Mary (as the ring suggests) is the perfect combination of enigmatic and amicable. Of course, she too is brighter than Watson. Speaking of Mary, the uncomfortable exchange between Mrs Hudson and Watson regarding her is hilarious. "I am not gay! Sherlock was not my boyfriend," Watson squeals to a surprised Mrs Hudson. Surprised because Watson wants to marry a woman.
3. The different explanations Sherlock gives for his survival. Going by his short conversation with Anderson -- 13 possibilities. By the way, don't you just love the senile Anderson? So vulnerable, so cute. *Cough* Anyway, Sherlock's 'death' seems to be something left for our scientific deduction or maybe a later episode? In any case, BBC breaks the Sherlock code by refusing to explain. I hereby pronounce this 'Sherlock Trolling'.
4. We meet Sherlock's parents in a blink and you miss situation. Unfortunately, I did blink. Not so unfortunately, I caught the bit where a befuddled Watson calls them...ordinary. Of course, they knew he was alive too. Poor, poor Watson.
5. Sherlock kisses Molly! And Molly has a boyfriend. And he looks just like Sherlock. Molly says she has 'moved on' too. Hmm.
6. Yes, there is a story other than Sherlock's comeback. But it takes the back seat. It climaxes at a fairly predictable point (clue: the climax leaves Sherlock and Watson in a life and death situation. I mean, come on!) and leaves one mystery to be unfolded. Actually, the episode tries to kill Watson twice. Just, why?
7. That one mystery drives the next episode going by this episode's sign off. So all isn't lost.
8. Text messages and social media do appear at important junctures. #SherlockHolmesIsNotDead is one. The other has something to do with saving Watson's life. Also, Mary can break codes. You go girl!
9. Lestrade hugs Sherlock. *sniff*
10. Sherlock turns into a cool biker. Now I've seen everything.
Now, for the slight disappointment. Sherlock spends more time in heroic revelry than scientific deduction. But then again, it is his comeback. Looking forward to intellectual orgasms soon.
Enjoy Season 3, folks!
And don't forget to share your theories about how Sherlock escaped his death in the comment box below!