"Should I spend 14 minutes watching this 1-ep. special?"
Well, it depends. Answer these three questions:
1) Are you pissed with how Mashiroiro Symphony ended?
2) Was your favorite character Sena Airi?
3) Do you like eroge?
If you answered 'yes' to 2 or more of those, then yes, you should watch this. However, if you only answered yes to one of those (or none of those), then this special will seem extremely boring. Sena Airi happens to be my favorite character from Mashiroiro Symphony, which also means I answered 'yes' to #1 (however, I don't particularly like eroge)
A thing to note: this special is not like the rest of
the anime. It is essentially a POV (point of view) type animation where you are the main character and Airi is talking to you. You guys are on a date, with this date being her first. Hence, this special is extremely eroge-like. But if you like eroges, that's great; this will perfectly suit your taste. On the contrary, those who puke at the thought of an animated erotic game should not watch this.
This is a fine special for what it is; nothing great, nothing shabby either. I personally enjoyed it due to having 2 of the "qualifications". If you have them too, give this a shot.