One of the best options at LAX
The Renaissance LAX isn't perfect but I think it's probably one of the better options at LAX. The shuttle is easy to catch to/from the airport and I believe it runs 24 hours a day. It's especially worth the wait from the airport as the cabs have a high surcharge. It is very close to some rental car options, but parking here is very difficult if you return at night. On one occasion, a staff member saw me driving up and down the structure hoping that I would catch someone leaving, and directed me to park in the spot reserved for emergencies. I appreciated that they helped me out but I assume there were some drivers who arrived after me and were out of luck.
The rooms are clean and adequate. A few times I had to ask for a new room as some have an incredibly strong scent of cleaner - a clean scent is nice, but this was absolutely toxic. Another time the room didn't have a chair. A couple of times the sink clogged up, but it was resolved soon after I called the front desk. A few colleagues complained about the noise of the jets overhead so it may be better to request a floor on a lower room if you are a light sleeper.
The lounge is nice and serves a good breakfast and evening appetizers. Breakfast is usually the same, but offers a lot, like pastries/muffins, bread, oatmeal, fruit, milk, yogurt, cottage cheese and a hot option, like breakfast burritos or eggs. Coffee, tea, soda and bottled water are available anytime that the lounge is open. The lounge itself is comfortable and offers adequate seating, although it can get crowded during the busy morning and evening hours. 
The gym is good and includes treadmills, elliptical machines and bicycles. I think there is also a small weight room and a pool behind the gym. It also offers water, towels, headphones, and each machine includes a small television. I'm not sure if I just missed the peak times, but I never had to wait for a machine. 
I ate at the restaurant downstairs twice. It was pretty good; nothing extraordinary, but probably above average for a hotel restaurant. The breakfast buffet is pretty huge but I think the main difference between the breakfast in the restaurant and the lounge is that the former offers someone who makes omelets on request. The dinner I had there was decent.
The best part about this hotel is the staff. They were always friendly, remembered me (I traveled and stayed there on a weekly basis for a few months), and a few times comped me lounge access before I had status. They are always welcoming and helpful. The valet personnel were great and flagged a taxi for me when I needed one. Being a business traveler, I had to pay for taxis with a credit card, which the drivers *do not* like, so the valet personnel would ask them if they would accept a credit card before I got into the cab. It was a nice perk instead of me having to have an awkward conversation in the cab.
Overall, I would recommend this hotel. It has its issues, but the staff goes out of their way to make you feel comfortable and it is probably one of the best options in the area.