I've been using the Windows emulator CrossOver for quite a long time. Actually, quite a few of my blog articles (for example, THIS) show screenshots have been made with it and even more articles (e.g, THIS) have compatibility info with the tested / reviewed app.
UPDATE (19/Dec/2012): the iPhone version has just been updated. Now it supports MKV remuxing (just like the two-month-old iPad version reviewed below) and some other goodies. Full review HERE.
UPDATE (20/Oct/2012): I've also tested U.S. DVB subtitle (technically, Closed Caption tracks) rendering. The test file, as usual in my 1080i60 U.S. DVB MPEG-2 tests, was THIS MPEG-2 + AC-3 + CC file. (In the original article, I've only tested European DVB broadcasts, which use another technique for subtitling: bitmaps. In the US, technically, an entirely different, textual closed captioning method is used.)
Unfortunately, as you can also see in the screenshot below (see the annotated "Subtitle" group containing nothing), it didn't even recognize the CC tracks, let alone rendering them:
You may remember THIS article reviewing the previous version of the multimedia player yaPlayer. Back then, I've stated the player is indeed very promising, albeit in some respects still inferior to the best ones (AVPlayerHD, GoodPlayer, It's Playing, HD Player Pro, ProPlayer etc.) in the AppStore.
A brand new version has just been released with a lot of changes. An AppStore update page (also showing the update of some other apps):
As was easy to predict, the trend of (obligatory, see THIS) AC-3 (a.k.a. Dolby Digital) dropping from AppStore apps continued. It started with the (at least in one area) excellent titles Oplayer, GoodPlayer, PowerPlayer and BUZZ Player (last, dedicated article on the issue HERE) and now, the updated version of “8player” also dropped the support of this very important audio format.
At MacRumors, I've published a lot of tips on mass converting videos to make one's life much easier when mass-converting several videos at a time. In the article below, I present you them all in an edited, more verbose format.
1, Using batch files (or looping commands) with command-line applications
Some of the video converters (for example, Project-X or FFmpeg) (also) have a command-line interface (CLI). Should you want to mass-convert / mass-process a bunch of files in, say, a directory or of the same type, batch files can be of tremendous help.
Yesterday night, after the first wave of AC-3 support drop from iOS multimedia players, the MKV playback support scene has turned out (article) to be very dire: previously excellent MKV players (for example, BUZZ Player) were rendered practically useless by the combination of the drop of AC-3 and other problems – for example, BUZZ Player's inability to play any MKV file with a DTS or AC-3 audio file, that is, practically, 99% of the MKV's you may have.
The player I recommend (review; another, MKV-specific one), along with the (currently, not AppStore-based) AVPlayer(HD), the most for non-DTS (that is, mostly, AC-3) MKV's on non-jailbroken devices has been BUZZ Player - it has had one of the best MKV behind-the-curtains demuxing and hardware playback.
UPDATE (15/Nov/2012): answering a question HERE, I've elaborated on the tweak's ability to highlight (and, then, copy / cut) text as you'd do with a true mouse.
While some third-party Web browsers (particularly iCab Mobile) are way more powerful than the stock Safari iDevices come with, I still prefer the latter. The reason for this is simple: Apple, at least in the pre-iOS 6 times (I haven't tested iOS 6 in this respect), has strictly forbidden to activate (via a simple call to _setDrawInWebThread()) flawless, stuttering-free scrolling in third-party browsers. Consequently, third-party browsers scroll around Web pages in a visually really annoying way.