My limited experience with the X kit (from 4x4 club members in MI that were running it a few years ago) is that the springs are WAY soft and the shocks are pretty stiff. Good combination for flexing well, and riding good on the trail, but I think OME has them beat for handling loads and remaining well behaved on the highway. (Soft springs = handling not so sweet when loaded, even if the shocks are on the stiff side...) I have NEVER heard anyone badmouthing OME suspension, excepting people who wanted more lift and were disappointed that OME doesn't offer a 4" kit. I would consider the OME kits more suspension enhancement than just "lift kit". They understand vehicle dynamics, load distribution, ride frequency, etc.
For comparison, I'm running the second stiffest TJL rear springs with Nth Degree (now AEV) coil re-locators and what amounts to a ZJ V8 front spring with an extra rubber isolator for an XJ, which stacks well with the TJ isolator. (For some reason the XJ isolators stack and the TJ ones don't.) I'm running factory gas shocks, but I'm bucking up for OME's this summer because I'm sick of the ones I have. (Too stiff!) My rates are very comparable to the HD OME rates, and load is not a problem, nor is flex!
Chris