Hey 88! Long time, no see..
So far, there are only "pros" to getting my i7. I have yet to see a flicker, do not have any issues with loud fans, and have been checking regularly on the heat on the aluminum by simply touching it. It isn't running hot at all.
I don't have omnisphere yet. I think I'm going to hold off on getting that one. Like Rounik said, sometimes you can get very overwhelmed with too many things to play with, and I have been working with Tone Gladiator 2 for a bit. That's a good one.
I also decided to pass on the Absynth. I didn't quite like the sounds nor the complexity of the synthesis modules. I got the demo and it didn't quite strike me as something I'd use often with my particular style interests. Now, Alchemy, on the other hand, is the one I chose.
That synth fits me well. I know very little about sound design, but it's interface and capabilities somehow just "click" with my thought process. Plus, it has features that no other synth has which I am going to use fully for a good while. Perks of being a college professor also allowed me to grab it with the educational discount, which is a nice bonus. Alchemy just makes sense to me. Can't really explain it.
Ozone 4 is a really nice little plug. I used that instead of the multipressor/limiter bundle within logic and the results were quite pleasing. The interface takes a bit of getting-used-to, but it has lots of nice little mastering "reminders" that aren't apparent with Logic's own plugs unless you know you have to use them. For example, it has exciters, loudness, EQ, limiters and a whole bunch of other important, useful mastering tools wrapped into one window. The presets alone within each segment are great starting places, considering they have provided several different types within specific sub-genres of musical style! For example, they have a good number of specific mastering presets just for electronic/dance. So to answer your question, does it make a difference in sound? I would say no, because you can most likely get the same results with Logic's own plugs if you are skilled enough. It does, however, put everything you'd use into one plug, which makes it much easier to develop your own personal process and execute efficient workflow habits. In other words, you'd be hard pressed to "forget" something while you're learning and crafting the art.
I also have the RX, which is really amazing if you need any audio-fixing to be done. Just for kicks, I recorded the TV on CNN or whatever, and was able to extrapolate the voices to a fine degree without the hiss and ambient noise, as well as the bumps and clicks from the mic found during real-time recording. I got both Izotope plugs for $250 because I signed up for the Mastering Audio class through Berklee online. They have a special deal with Izotope so it was definitely worth it. (Of course, the class is $1K for 12 weeks, but I thought that was worth it too...)
Anything else you need to ask, let me know! I'll try my best to help!