DON'T MISS YOUR BUS. For the sweet love of all that is delicious and good, do not miss your bus. Be there at least 15 minutes early so that if you're late, you're still on time! I missed the bus for a Vegas to LA by 5 minutes and bam, it was long gone. This meant trying to transfer my paid reservation ($5 charge, credit card only and their machine was down) and then waiting on stand by while the next bus 4 hours later was filled with customers. If it's full, you won't get on!
As for the ride itself, it was like being in a clean charter bus. The chairs were a little tight but comfortable, each seat had an AC outlet that worked like a charm. The AC was good and didn't make the ride feel stuffy. I thought it was cute that the roof was see through- you can probably have a nice storm watch if it were raining. Wifi was super slow but working.
Your luggage is loaded underneath the bus and tagged if there's two stops (riverside & LA, for example) but if you bring something small, you can try to fit it under your chair. I had a duffel that I kept with me and was thankful I didn't have to wait for them to unload my bag. The ride was almost 4.5 hours from Vegas to Riverside (downtown metrolink station) with no stops.
Still cheaper than flying or driving on my own, so I would seriously consider taking this for future trips! Go megabus!