I've waited for 11 years for Vegas to get a place like this. For the most part, it was worth the wait. I have yet to see a concert here, but season tickets to hockey have made me a regular at T-Mobile. I also saw UFC at T-Mobile and thoroughly enjoyed it. Here's my take:
Pros:
Rollin Smoke!
Beautiful arena
The Park area outside is unique and fun
Security to get in is fast
Cons:
Not a lot of restrooms
Drinks and food are outrageous
The new Uber pickup for the arena is stupid. At Excalibur!
Given the prices of food and drinks (expected in Vegas, but still), I suggest eating nearby before your event. All things considered, T-Mobile is a great addition to this city and the Las Vegas strip.