I loved this episode, though the feels were a bit muted for me because they telegraphed time-travel really hard at the start, so from the moment Barry saw himself and they focused on obvious time travel markers like the lady hailing the taxi I was like 'well, nothing from here on is permanent.' I kinda wish they could have had the time travel be more of a surprise so that I could have actually felt the feels that they wanted me to feel, rather than just thinking 'Oh, he's paralysed? Good thing this isn't real. Oh, he's dead? Guess I won't see him until next week.' However, giving us as the audience a decent bit of background on Wells/Thawne was cool, otherwise, I'm mostly just looking forward to seeing the coold ways that Barry acts now that he has foreknowledge of events (e.g. not spilling his drink all over Singh)
I also don't think that anyone whining about retcons understands what a retcon is. A retcon is retroactive continuity, a time travel story where they knew what was going to be changed going in is not a retcon since there is no retroactive behaviour, it was all clearly written to not be in continuity going in.
I have to admit, Barry is beginning to badly suffer from plot over intelligence when facing bad guys and failing to take them out. Thing is, the second time he had to save, Singh, giving Mardon the time to escape, however the first time, in the car, they should have injured Barry and had him speed healing while Mardon escaped, instead of just cutting away with no explanation.
I have to say, most of my complaints are thought through post show, so I did enjoy it more that I might seem to while I actually watched it. Just saying, this won't be half as enjoyable on a second viewing.
P.S. I'm really glad this episode got delayed and we didn't have to wait for the conclusion over the hiatus as I assume was initially planned.