Due to my limited knowledge and understanding I wouldn't touch the controversial part of its celebration.
BUT I do feel tempted to address few important aspects of such celebrations which I have come to know from different sources.
Naats being "sung" on the tunes of old Indian songs and people in the crowd almost dancing to those tunes (left right movement) That can't be called Waj'd. It is not their fault, those naats are sung in a way that excite people which doesn't seem appropriate. I even know some people who can point out the specific Indian song 20-30 years ago on which a new naat is based (For GOD sake, if one is so willing to celebrate it, why not recite the naat of the Prophet (saw) mentioned in the Quran)
SOOOOOOOOOOOOOOO much emphasis on the songs based naats all night, almost negligible sharing of knowledge through hadiths, recitation of Quran,....etc. The prophet (saw) encouraged more sharing of hadiths and reciting Quran then singing naats...
I heard that it is kind of a fashion show for some women, (with all the make up of the world, along with dresses that attract men in the crowd). All the emphasis on covering the head and less dupatta on the low necks that require more covering...etc. (Sorry for the language, but heard it from people I know....)
I might be wrong in some places. In that case Allah (s.w.t) may forgive me. Allah (s.w.t) knows best!
I have been attending milads pretty much all my life and I yet have to see women dressed in low neck or without dupatta in milads. Also mostly milads are segregated. Even if they are in masjid, there is a division b/w male and female section. People do dress up nice on milad and why wouldn't anyone wear nice clothes...anyway I don't think there is really any fashion parade going on in milads. Also milads are not naats naats, and naats... Hadees and different aspects of Prophet p.b.u.h are are shared, people do read Quran...different surats like Surat-e-Yaseen, etc. Sometimes people do reads naats on the tune of songs and that is not quite right and yeah that should be discouraged.