Not mine, but Johnny (at Wild Horses) has had his up near 9000' in the Sierras and to more moderate elevations in southern CA and loves it. It acts like any normally aspirated EFI setup would. You won't retain all of your sea-level power, but unlike a craberater, you hardly notice the elevation changes any more.
Turbos and superchargers take care of the rest, but in lieu of one of those power adders, computer controlled EFI is great. Even the simpler TBI type like we're discussing.
Same thing I've noticed on other EFI engines. What used to really tax a lower-powered heavy vehicle (namely, climbing the high mountain passes on the highways), no longer seems to deserve much notice. At least not as much as before.
Hopefully others that use theirs more often will have more confirming feedback for you. Interested in any not-so-positive experiences too.
Also be interested to hear if anyone has used both stock and aftermarket air-cleaners and noticed any difference.
Paul