I started out the same way: I never thought I'd be interested in the show either, seeing it as just another internet phase a la
Panty and Stocking. However, I stumbled across a TF2 micspam with "Giggle at the Ghosties" playing, and loved the lyrics enough to look more into it, until I found myself a brony.
I like this show for all the reasons stated above: clever writing with subtle bonuses, a strong, diverse, female cast whom can be sympathized with, and a cheerful idealism normally absent in cult classic cartoons. At the same time, it doesn't attempt to be anything more than what it is: it realizes it's a show intended for girls, and acts accordingly without sinking to the pitfalls of pandering, materialism, or gratuitous cuteness. Also, the character designs are too cute. Overall, it shows that cartoons can still be enjoyable in an age where shows like these are few and far between.
Trying to convince others that it's better than what its premise suggests is moot, as no one unfamiliar with the show would take colorful ponies seriously- and I wouldn't expect them to. It's entertaining seeing how some overreact to the whole phenomenon (i.e. writing essay-long rants about how twenty-year olds aren't allowed t enjoy a cartoon intended for young girls), though.
I've only heard of the details, and that's all I want to know. Rainbow Dash does make a good butt monkey, however.