This will be a fairly short review, because I mostly want to talk about one thing which I've seen nobody talked about it in their reviews. This review WILL contain SPOILERS, read it only if you've watched the series.
This series had a very good start in my opinion, and could've easily became a really good romance anime. This didn't happen, and the main issue of why not is because the whole amnesia thing.
If you make a little research you'll find out that the proper name for the amnesia Tada Banri has in the series is Retrograde Amnesia (which is also written in the Wikipedia page for "Golden Time", but whatever), and now you'll ask, "What's the problem with that?", the problem, which I'm very surprised nobody talked about it, is that to "cure" this type of amnesia it's not enough to simply be told personal experiences and/or his identity, -which in Golden Time is well done, Tada Banri didn't suddenly remember everything when Linda told him stuff about the past- instead this amnesia can be and is usually cured due to "Spontaneous recovery", which is described as "Spontaneous recovery is the reemergence of a response that had been previously conditioned", which basically means that he (Tada Banri) would eventually remember all his past due to the fact that he already lived it, which we all now that that happens in the last moments of episode 23.
Not seeing the porblem? The problem is that the only cure for Retrogade Amnesia, mentioned in the paragraph above, doesn't make the person (Tada Banri in this case) forget magically what happened after his injury (the motorcycle in the bridge thingy in Golden Time). What i'm saying is that when Tada Banri recovers his memory (possibly due to Spontaneous Recovery (because there aren't other cures to this amnesia)), he shouldn't have forgotten the year and a half he lived in university, instead he should've kept being Tada Banri (with his university memories) but also with the memories of the past. And this is a big mistake. A very big mistake. If the amnesia thingy would've been secondary in the plot, I could've forgiven the problem. But it isn't secondary.
The motor which develops the story of Golden Time is the amnesia, almost all drama the show has, conflicts between characters, entire characters, everything, revolves around the amnesia Tada Banri has, and if it doesn't have logical sense, how can this series have sense in itself?
Apart form that, which was the main issue I had with the series there are other things which bugged me, whole episodes in which nothing important happens (they feel a littile... filler), underdeveloped secondary characters (what happened with Oka and Mitsuo anyway?), bland main character (apart from the amnesia thing he has no personality), overly dramatic characters (which is also an issue in Toradora imo xD), completely "invisible" OST... and so on. I'm not going to talk about this things because there are already people which talked about them in their reviews (and I don't want to make any longer this review), instead I'm going to talk about what I liked in this show.
The male main character, aka Tada Banri, was a disappointment for me (with the charismatic MC Toradora had, why couldn't this show had someone like him?); Koko instead, was an excellent female main character for a romance (better than Taiga imo), atypical, doesn't fall in any -dere archetype and has nice moments throughout the series. From the secondary characters 2D-kun was the best one, sadly it didn't have much screen time :(
Art was fairly decent, although for an anime from 2013-2014 it wasn't exceptional, but the animation for the OPs and EDs I found them brilliant, colorful and bright. As I said, the OST is like it didn't exist, but the OP/ED music were decent (especially the second OP and the first ED).
What I liked about the story, is that it's not your typical romance which ends with a kiss (if you are lucky), instead explores (not very well sadly) the afterwards of the relationship (similar to CLANNAD AS, Nazo no Kanojo X and some others). The end could've been better (closing some loose ends), but still, it wasn't bad either, predictable from the first episodes though.
Story: 6
Art: 6
Sound: 5
Characters: 6
Enjoyment: 7
Overall: 6 (which in my list translates to a 7 because of my rating system)
Final notes: A nice anime to watch, which if you are a fan of Romances I recommend you seeing it, but don't expect something great, because you will probably be disappointed. I don't regret at all watching Golden Time, but I probably won't watch it again.
tl;dr: This anime could've been better if:
A. the amnesia thing was thought better.
B. the amnesia thing wasn't in the show.
C. the amnesia thing wasn't something in which the plot relied to move forward.