This manga has been marked with the "Rushed Ending/Axed" category tag, and for the first time in my long manga-reading career, I can't make up my mind whether to vote it up or down. I think that in itself attests to (G) Edition's greatest flaw.
The characters are loveable and the premise is creative, but the story suffers from a severe lack of direction. It's episodic with a slice-of-life/school-life feel, plus an underlying goal re: Aruto's setting off on the path to becoming a (hentai) mangaka. Yet at the same time, Kawashita Mizuki seems to forget about that for chapters on end wherein she keeps making up more and more crazy futuristic gadgets and rules about time travel, with seemingly only one clear motive in mind: to shoehorn in as many ecchi scenes as is humanly possible.
So basically, the "plot" meanders around, touches on a couple of interesting topics, shoves fanservice in your face every other page and then abruptly comes to an end. So I can't say I'm disappointed about the length, considering how doubtful it is that the story would have progressed even if its run had continued for another 5 volumes.
Overall, I don't regret reading (G) Edition at all, because it really was a lot of dumb, innocent fun, but I'd recommend it only if/when you're in the mood for ecchi and comedy with a dash of soft sci-fi on the side.