My review (cross-posted):
Although this episode was conceived of and written to be the pilot episode for the series, it feels much more like a direct sequel to the Arrow Season 2 episodes "The Scientist", "Three Ghosts", and "The Man Under the Hood", and I actually think it makes the episode work much better than it otherwise might have. There are definitely moments when it does feel like a pilot, but that's to be expected since the writers couldn't have expected that everyone who watches the show will have seen the above-mentioned Arrow episodes.
I really liked the way the writers structured the episode narratively, starting out in the 'absolute present' before essentially giving us an extended sequence of flashbacks, first to Barry's childhood and then to events that were clearly meant to take place during the events of the Arrow episode "Three Ghosts" (which was a nice little 'easter egg' for fans of Arrow), and then flashing forward (no pun intended) to show us Barry's 're-entry' into the world and the way that he discovers what the explosion did to him and others.
Character-wise, I like that we've got a nice diverse group of people who all have different roles to play in the story, and figured I'd offer up a few thoughts on each individually:
Iris
Iris is clearly meant to be the series' 'Laurel' (the girl Barry can't have), although she also reminds me a little bit of Thea since there's very much a brother/sister-type vibe between the two characters. It will be interesting to see what they do with her going forward, and how long it takes her before she actually figures out that Barry's pining for her and that he's now got superpowers (because she's going to have to eventually, especially given that her dad's in on Barry's little secret).
Detective West
He's clearly meant to be an analogue of Arrow's Quentin Lance and John Diggle, serving as both the series' lead civilian law enforcer and as one of Barry's chief confidantes, and this combination of roles is going to be something that I think will help keep the character from getting lost in the shuffle, which seemed to sometimes happen to Quentin.
Caitlin Snow
She seems to very much be the series' analogue to Felicity, but she also reminds me quite a bit of the characters of Alfred Pennyworth and Barbara Gordon (particularly the version of that character seen in the 2002 failed WB series Birds of Prey). It's going to be interesting to see where her character goes and whether or not the PtBs have plans to use her supervillain alter-ego from the comics or if they opt just to keep her as one of Barry's civilian allies.
Cisco Ramon
He doesn't seem to have a direct analogue on Arrow, although he does remind me quite a bit of Xander Harris from Buffy the Vampire Slayer. It will be interesting to see if they give his character more to do in future episodes besides just being the 'techie' behind Barry's 'toys and gadgets', because I think there's a lot of potential there for him to fill a sort of Robin-esque role in Barry's life, either in a civilian capacity or in the capacity of his superhero identity from the comics.
Harrison Wells
He strikes me as being the series' analogue to both Malcolm Merlyn and Slade Wilson, and it will be really interesting to see how he's used in future episodes. I also think there's a real strong possibility that he's being set up to become the series' version of Professor Zoom/Reverse Flash, even with a character whose name is clearly derived from that character's comic-book alter-ego (more on this below).0
Eddie Thawne
This character's name is clearly derived from Eobard Thrawne, the comic-book alter-ego of the above-mentioned Professor Zoom, but he seems much more likely to be the series' analogue to Tommy Merlyn in that he's there to be an obstacle to Barry and Iris being together. He also reminds me somewhat of Harvey Bullock from Gotham, albeit without Harvey's darker edge. We'll see where the writers go with his character in future episodes.
In terms of recurring characters, I'm interested in seeing where they go with Henry Allen; he seems to be set up as the series' analogue to Moira Queen, but given that Susanna Thompson was a series regular on Arrow and he's only a guest star here, I'm not entirely sure how much involvement he's going to have as things progress, which is kind of sad because I like the relationship he has with Barry and am interested in seeing more of his background. Captain David Singh (who seems like the other major recurring character introduced in the episode) is hard to get a read on because I don't know if they really needed him in the episode, but we'll see what happens.
Somebody above complained about Oliver Queen's cameo in this episode, but I personally think it was a nice touch because it allowed the writers to do something that is kind of crucial for the series as a whole - explaining/offering context for why Barry does what he does going forward - in a non-traditional fashion that also paid homage to the fact that the series is part of a shared universe (it reminds me of the way that the writers on Buffy the Vampire Slayer reminded viewers that it and ANGEL were connected without having to actually do explicit cross-overs between the two series). I did wonder why Oliver wasn't wearing the domino mask that Barry gave him, if only because it makes me question where the scene takes place relative to what's happened/will happen on Arrow itself.
I do wish I'd been able to re-watch the 3 Arrow episodes that serve as sort of a precursor to this episode, but that's only because I'm a bit of a completist nerd; the episode stands very well on its own, and was a nice way to set up the series going forward.