Features - it's a phaser on steroids. It has 4 independent phasers all switchable and volume-adjustable. Each one can have LFOs applied to pretty well every parameter, and ALL of the LFOs are independent (you're not just stuck to a limited number of LFOs that you have to use for more than one parameter!) which makes for 50 or more LFOs - I've never counted, but it's an immense number. It has controls for the phase, several for tonal control and a bandpass filter, pan, speed, feedback - all the usual things, but the level of tonal control and the LFOs are what really make it stand out. You can tailor the frequencies to fit into your mix very accurately - most phasers just phase up and down the whole spectrum, but not Mobilohm - it has very precise tone control on each phaser, and then a global tone control. The LFOs make it useable as a general-purpose filter not just a phaser. You can get gated phasing, rhythms within the phase or the speed of the phasing itself. Set some of the parameter LFOs to extremes and your end sound bears no resemblance to the original - on a simple drumloop you can get huge booming kicks followed by high squealing snare resonant blips. Then randomise it and you have complete chaos. And because there are 4 phaser circuits, you can use it to split the whole thing into 4 frequency bands to get it to sit in a mix - 1 for phasing lows, 1 for mids, 1 for high mids and 1 for highs - then switch the circuits in and out (automatable) change the rhythm of the LFOs and you can have a whole piece of song playing from just one source sound. It really has huge capabilities which many people I suspect only just touch on every now and then. The other side is that you can actually use it as a standard phaser! Sounds lush and thick, or thin if you want it to. There is no type of sound that it can't be used on at some time. It has no audible glitches unless you program them in deliberately - another Ohmforce feature that's common - excellent audio quality. It might be worth paying extra for the pro version with full midi - there are so many features that you may want to automate, it can be difficult with only VST automation (but another good one is that they allow you to specify the order of VST parameters priority - so if you can't automate what you want - go in and customize in the subedit page!) Plus you get more than 16bits with the Pro Mobilohm - though to my ears I'm perfectly happy with the 16bit limitation.
The reason I marked down the sound a little is that it can sound a little digital when used as a basic one channel phaser - it can sound lush and rich, but you generally have to use more channels to achieve that - but it's a very minor complaint - it can vary it's sound as much as you are prepared to put in programming effort.
Not for the faint-hearted if you're unsure about in-depth programming, but you can't go too far wrong by just turning knobs at random though. Flexibility=complex