I was in Vegas earlier this week, but I only took I-15 as far as downtown. That whole area is a mess with the construction, especially if you happen to hit rush hour traffic. There were some lane diversions and lane closures while I was out there, but it's an ongoing process so you have to check the latest reports each day.
NDOT has a site for Project Neon with the current traffic alerts/closures and maps...
http://ndotprojectneon.com/know/traffic-alerts/I didn't get a chance to drive out to Pahrump/Crystal, since this was mostly a business trip. Although, I did have some free time to see some shows and drive out to Red Rock via I-15 to NV-160 which was clear sailing without any roadwork going on.