Unfortunately it's a pretty average app by todays standards. There are a number of great video players that have been in solid development since VLC was pulled.
I'd imagine speed would mostly be dictated by ffmpeg as that's what everyone is using.
I haven't checked with this version of VLC, but can it do hardware h264 inside an MKV container ? That's where some players have put in a lot of work to hardware decode MKV (when it's h264) as iOS requires some crazy workarounds in that area. So if VLC is doing MKV in software, it's still going to appear slower to the user.
Also, I'd say Open Source isn't really a relevant feature on the app store.
Quite a few of us are running jailbroken devices, and can run just about anything we please.
Additionally, it costs a one time $100 charge to become an Apple developer (assuming you already have a mac), and then you can deploy everything even without a jailbreak. Given that a new device costs upward of $650 (let's ignore "subsidies" here), another $100 to get locally "open" the device is, for some of us, a reasonable expense.
