I've test-driven both but do not yet own a 4R.
There is a definite difference when cornering with XREAS. The truck remains almost completely upright during the turn (with little noticeable dip) and in that moment feels like a much stiffer suspension that would normally give a rough ride to due tension.
The beauty of the XREAS is there is no rough ride out of the corner as the suspension only "kicks in" during a corner (or a similar challenge).
I personally am not going to buy a 4R without XREAS. I think it's safer and dramatically more comfortable when swerving around traffic, cornering, etc.
That said, if you don't buy it, you won't really know what you're missing, as the stock suspension does a fine job and the truck handles well across the board.
I'm leaning toward a Sport, as it comes with XREAS already and the only thing that really defines a Limited is the Nav system. With technology changing so quickly, I don't want to be married to a NAV system that will be outgunned in a couple years, and that Toyota might not support as long as I plan on owning the truck.
Garmin just brought out the GPSMAP 396, which has land, marine, aviation modes, and includes an XM satellite radio, whose signal also gives it a REAL TIME WEATHER RADAR display! For $2500, that's a MUCH better buy than paying $4000 more for the wood panelling in a Limited.
If the price is right on your Limited, though, it might make a difference. Also, you should note the only way to get Leather on the Sport may now be aftermarket.
Dave.