I'm at my wits' end. Installed it (trial version) on a clean Lion (10.7.4) on an iMac (500G HDD, 3.06 GHz c2d late 2009 model with 4G RAM).
The remux of "Iron Sky" (main, 16 GB MKV, 5 audio tracks and no subs, direct BR rip done by myself) iFlicks took 34:00 (of which the last 10 minutes was spent on the two final steps: muxing and streaming-friendly conversion). The same file could be converted by Subler (on my other Mac, a 2.8 GHz late 2009 MBP 17" with Vertex 4 SSD) in 6:58 (that is, about five times faster) and by MP4Tools in 20:20.
This isn't because of the HDD vs. SSD - iFlicks behaves in exactly the same way on my SSD-based MBP. Running Subler off a 70...90 Mbyte/s internal HDD would have resulted in at most a 50-80% increase in running time.
Do you think it's because it's a trial version? I won't shell out $20 for an app only to find out it's very slow and can only be used in some special cases when Subler is plain incompatible with the video I want to convert. If the registered version is as slow as the trial one I mean.