Hi,
another way to inport .las file is to convert it to .txt file.
I use lastools, open source tool available online.
convert las to txt extracting x,y,z and other data you need in .csv format
then add a header using txt editor e.g. x,y,z,i
import .txt file to arcgis
plot x y point
export data and save as .shp
for large file importing and savisng in arcgis might take some time
Regards,