1. Between Arrow, Gotham and the Flash, DC-live action has found a winning formula, I think. Offering long-running soap/mystery arcs, strong stunts and action, and loads of Easter eggs for comic book fans in a slick, pretty people package. The trick now is to make each one distinguishable from the other, lest they become the CSI/NCIS/Law & Order of the superhero set. If Gotham went darker and more violent than Arrow, Flash goes the other way, with a lovable loser as protagonist, more Peter Parker than Oliver Queen or Bruce Wayne, and a focus on super-powers rather than street justice.
2. I could have done without the "murder of Ma Allen" element, but given Geoff Johns' involvement, this was inevitable. Because the fans know who the Reverse-Flash is supposed to be, the show counters with two characters who could turn out to be Professor Zoom. This gives Barry a long-term goal, more to free his unjustly-convicted father (played by the 1990 TV Flash, John Wesley Shipp, cool!) than to get revenge. More interesting is the shared origin of all the powers. Smallville initially tried something like this with the stupid Kryptonite poisoning angle, but here, the explosion of an experimental particle accelerator works quite well. The Flash's original stories were about science, with villains representing forces of nature/physics just as much as the Flash was. The explosion gives the show license to create all the Rogues, but also characters like Firestorm (announced), Killer Frost (in play) and Vibe (him too).
3. While I waited for Barry to finish his run in Arrow, you don't really need to. The pilot works without it, and it's even strange to think Barry takes off for Starling City somewhere in there, near the beginning. It's not mentioned. And poor Felicity Smoak, how can you carry on a relationship with the Fastest Man Alive if he's got a massive crush on Iris West on his own show?
4. The costume's fine, and I don't have a problem with it, but I'm not enamored of some of the effects in running scenes. When he moves faster than we can follow, it's cool. When the camera stays on him and the background speeds by, it looks a little cheesy and green screeny. I'm sure these issues will sort themselves out over time.
5. They didn't wait before giving Barry a support system of people who know his secret identity. As with the 1990 show, there's a whole science team helping him learn to use his powers, just like Tina McGee did back in the day (I hear Amanda Pays is set to appear some time, perhaps as the same character?), and Captain West, Iris' dad and Barry's de factor father figure, is already on his side. They slowly brought people in on the secret on Arrow, so there's no reason to repeat the whole cycle. Let's just set up the board and go from there.
6. For a simple "assistant", Barry is a really brilliant CSI (he's his own Felicity), with Sherlock-like graphics appearing as he analyzes clues. Well hey, it's a fun device, even if it's derivative at this point. On the whole police/detective front, I could do with a busier police station, but did smile at the Weather Wizard's crime - just bank robbery. That's the kind of crime the Flash should be dealing with.
7. Some people have complained there were too many night scenes, making the action dark and murky. I don't think it was too bad, but since the show is filmed in Vancouver just like Arrow, I'd like them to keep the two worlds distinct by making Starling Vancouver at night, and Central Vancouver during in daylight.
8. I say Central City, but an aerial view and references to Keystone City - the Golden Age Flash's city and later, Wally West's - is right there across the river. So there are Twin Cities to explore, and they hopefully each have their own character.
9. If Arrow is cool by virtue of all the DC characters showing up or getting referenced, The Flash goes into overdrive with the Easter eggs. Is it too much? Not for a pilot, because a lot of it is seeding future events. Grodd's open cage. The aforementioned Reverse-Flash. All the name characters that, as was done with Arrow, are destined to become metahumans. And that squee-inducing (and much-spoiled) reference to Crisis, an event that will forever be connected to the Flash and that also hints at Barry perhaps one day breaking the time barrier. Throw in Linda Park, am Arrow cameo, company names from the DCU, a magazine called Science SHOWCASE, winks to the 1956 Flash origin and classic Flash stunts, and you've got a lot of fun stuff for the fans that won't have wider audiences scratching their heads.
While none of the DC-related shows on the air fill me with passion, all of them are fairly solid action thrillers coated in comic book candy. I don't consider any of them revelations or must-see TV (which is why I DVD-wait Arrow), but they entertain me, feature mostly likeable actors/characters (Flash doesn't have a "Laurel" at least), and keep my interest. I can probably be counted on to watch the first few episodes at least, and to buy the DVD next year if I don't get very far.