Alright, here's my take.
Da Good - Let's start with the pros. The animation was fantastic. The movements and expressions had good chemistry, each complementing each other. The artstyle itself wasn't bad either. It uses the typical 2010 CalArts style, but it adds a nice twist to not look totally unoriginal.
Da Bad - Unfortunately, the writing is where the two episodes failed. They were so cliche and by-the-books. Nothing stood out whatsoever. The episode with the pony, for instance. The humor itself is pretty hit-or-miss, leaning too much towards miss. Some were especially cringeworthy. And while Star and Marco's relationship is endearing, I could get the exact same reaction from Gravity Falls, a much more consistent series. I'd put SvTFOE above GF animation-wise, but below GF in writing and character dynamics.
Da Meh - The characters, I've seen them before. Blah blah blah, dorky teenage boy, blah blah blah, sassy annoying side-character voiced by black woman, blah blah blah, incompetent big bad. The only character I hated was the pony, but everyone else was simply...meh. Although Star isn't as annoying as she could have been. She's surprisingly levelheaded for someone as wacky as her. But I'd need to know them more to care about them.
Verdict: There's some good aspects here, but the overall experience, I did not enjoy. It needs polishing in order to truly be good. Until that point, despite the great animation, it's flawed at best and generic at worst. 5/10