Just to put in my two cents...these are fantastic recordings...there's really nothing like them in drum corps. The new disc is wonderful and if you aren't familiar with isomike and the work with BK or Troop it's tremendous stuff. Highly recommended! A shame that the Troop and BK shows from 2009 weren't recorded...I was actually looking forward to the isomike take more.
Having said that, crowd noise is fine, but I don't find it central to the experience of listening to a well-recorded performance. The corps itself has to come through as life-like as possible or it's mostly a non-starter for me. Indoor recordings of drum corps are usually horrid, although the principle exception where they work would be when I might be desperate to hear a show and will willingly throw down $ for a compressed MP3 of whatever gets posted. That doesn't mean I'd prefer it. It's sort of like having those 1995 recordings--I think they're awful, but they're all we have available.
Drum corps and symphonies have a lot in common as far as recordings, IMO. With a high-quality recording, I don't particularly need to hear the crowd go crazy at the end of the show, or at big hits in the performance. The music and the performance themselves are riveting and the recording allows all of the subtle nuance to be gathered and enjoyed. The only exceptions to this for me are where the crowd becomes part of the moment...where it's a phenomena, like (especially) 2008 Regiment. Though a super-clean full-dimensional recording of a show like that would have its own value in addition to a "live" recording. Another example--I prefer the "studio" recording of the 2003 Regiment show.
If DCI were to offer studio recordings using near-obsessive techniques like those employed by isomike, I'd certainly buy them. Have isomike record whoever's passing through the area each summer? That'd be something!