I've tried Ubiquity a couple of times. It is a simpler take on the D6 rules, but be prepared as it plays on the rules of averages. The average dice roll will give you 50% chance of rolling successes. You roll 6 dice for example, and the chances are you will get three successes (a 4+ roll on each die) 50% of the time. It also means that you require higher level of dice in skills, compared to other D6 variants, to actually be good at anything. One variation of Ubiquity I've played keep the pips from D6, and the pips can add to a single die in the dice pool to bump up the die result. For example, if you have 3D+1 in a skill and you roll 3, 4 and a 6, you can bump the 3 to a 4 by using the pip to gain that extra success.
The rule on wild dice also depends on the variation of the mechanics you are playing. One version will allow you to keep rolling until you stop rolling 6's, with each roll of 4+ being counted as an extra success. Another variation is a roll of a 6 counts as a critical success, whereas a roll of a 1 counts as a critical failure, wiping out any successes you have rolled on the other dice. I know the new 40K RPG Wrath and Glory is a take on the Ubiquity system, and has it's own set of wild die mechanics.
To be honest, as it is meant to be simpler than WEG D6, overall I find Ubiquity rather convoluted for what it is. There isn't a stand alone Ubiquity rulebook either, which means that if you wish to try it out or buy the rules, you need to acquire a copy of a core rulebook for one of the games using it. From the two I've read, to familiarise myself with the rules, the settings were utter rubbish. This means you end up with a rulebook that just will sit on your shelf, and this is probably why there is little love for Ubiquity. The best way to experience Ubiquity is use one of the WEG D6 core books, such as D6 Fantasy, and just change the dice mechanic.
I have only tried a Ubiquity engined game once when I played Space 1889 at Continuum. I don't remember anything outstanding about the system. It was functional and faded into the background, letting the story shine through. I really should read the new 1889.
Thread Necromancy! From prepping for Space 1889, and then running it at North Star, I've found myself rather liking the system. It's very light and easy, with just enough detail to matter. It runs quickly and smoothly, even with a group of six players.
My only issue is attacks and damage being folded into a single roll, but it was an issue in theory rather than in practice, and scale (as seen in a dinosaur fight) worked out just fine.
I can see myself doing more with the system, whether in Space 1889 or elsewhere.