I have the traditional series, the X series, as well as Blackouts. Some general impressions:
Output - Blackouts are by far the hottest (a bit too much IMO), followed by original EMGs, and finally the new X series. Still, I think the X series have plenty.
Clean tone - definately better cleans with the Blackouts and the EMG X series as compared to the original EMGs. I like the cleans on the X better than the SD's - probably due in part to the extremely high output of the SD's. I think the X's have a clearer, chimier top end.
Dirty - they all work pretty well in this regard. I would pick the X's if buying new, but I wouldn't replace all the traditional EMG's in my other instruments. The originals are still pretty cool for gainy stuff. Blackouts are cool as well, but I prefer the high end on the X's. I prefer the original 85 in the neck (seems smoother - more "woman" tone), to the new 85X, and I was least impressed with the SD neck pickup.
I find the X's to be the quietest of all three pickups.
The tone control on the X series seems very subtle - I don't care because I don't use them, but they don't seem to do much.
Solderless install works well though one of the plastic parts of the pot to pot connector cracked. I don't mind soldering so I would prefer the original system just to eliminate any possibility of bad connections/durability. I like being able to use the same system for the EMGs and Blackouts - I wish you could do that with the X series. They aren't drop-in replacements if you have tone controls.
In summary, the X's are cool, but I think they may get overlooked due to the fact that they came out as a response to the Blackouts, and therefore may be viewed as inferior. They sound killer in my PRS (check out my Youtube clip), and I plan to put them in another SC 245 I have on the way. It's nice to have choices, and you will notice differences, the biggest being in the clean tones.
JR