if you're talking about an APP through the app store. i had no idea there was one. (and i would not be very likely to download an app and use it for access to subsim... Im just not a big APP guy)
if you're talking about accessing subsim through safari on iphone, i do that almost every day. the format is easy to use. though i wondered why the change was warranted because the desktop version of subsim worked just fine too and was what i was used to seeing every day anyhow.
honestly, it works just fine, and i dont really have much of an opinion about it one way or another beyond that i guess