The W Hollywood: Pay $$$ to feel like a nobody
The W Hollywood is a great place to stay in LA—if you're a twenty-something wannabe reality TV star with thighs the size of the average woman's wrists and Daddy's black AmEx. For everyone else though, you might want to think twice about staying here. It's essentially a nightclub with rooms which, were guests actually allowed into the nightclub, would be great, but you're not. Even with a room key, you and your party will be kept decidedly on the wrong side of the velvet rope. 
Physically, the hotel is beautiful (as are all Ws, in my experience). The lobby is stunning, the pool is attractive and our room was fun (it reminded me of something out of an Austin Powers movie) as well as comfortable. The staff were generally friendly and helpful and contrary to some other reviews here, we heard no noise whatsoever in our room even though we were on the 10th floor and so, not far from the nightclub. It's also in a great location, (literally) on top of a metro stop (Hollywood/Vine) and about ten minutes (slow) walk along Hollywood Bvld to the Dolby Theatre, etc. 
But the whole time I was there—we stayed 5 nights—I felt like the uncool little sister tagging along to the cool kids party and I think the hotel played a part in making me feel like that. This wouldn't be so bad except for the fact that I was paying for the privilege. 
The lobby (or the Living Room in W-speak) was constantly filled with a variety of posers, wannabes, etc., especially in the evening, but of course the hotel can't really control that and it is supposed to be a profitable business after all. But approaching the doors in the evening, we had to show the doormen our key before we'd be let in—and then do it again to get to the elevators. We stayed there over a weekend, and met many a drunken waif stumbling along the halls. I just didn't feel comfortable there. Honestly, I felt like I was intruding on someone else's good time, and shouldn't be there. When you stay in a hotel, all areas should feel like yours to avail of. I certainly didn't feel like that here. 
But the real issue with the W Hollywood is the nightclub/pool situation. The pool IS the nightclub, or part of it, which is not owned by the W but is a location of Drai's, who are also in Vegas. To access the rooftop pool (level 12, I believe) you have to go all the way down to the ground level to get in. There are signs in the elevators saying this is for "occupancy control" but really, it's for admission control. There is a special line for hotel guests, but no preferential treatment. On Saturday evening we approached the concierge about the possibility of getting into Drai's that evening, and he was (very nicely) straight with us: unless we forked out $550 for bottle service—with a rule of one bottle between every 2 people—we didn't have a hope. (Which made me wonder, who IS going to be in the club?!?!) We went to the lobby bar instead but one of my friends, undeterred, decided to try to get in anyway. She spent 55 minutes talking with various members of staff before being finally allowed in for the last 30 minutes of the club evening, at a cost of $20. She reported that although the view of the pool was nice, the club wasn't even all that special. 
Clubs in W hotels are not unusual. All Ws have a trendy nightclub atmosphere to some extent. The W Times Square is a good example, but I've stayed there twice and have never felt like anything but a valued and welcomed guest. The problem with the W Hollywood is that their priorities are all wrong, because their priority is the club/nightlife. This is far from a cheap hotel and when you're paying a lot of money, you want to feel like the hotel appreciates that. Here, I felt like the hotel "belonged" to the people in the club and the lobby—who probably weren't even guests—and that I was intruding. 
I gave it 3/5 stars because you really can't fault the decor, the cleanliness or the location. But if I were the management—and especially if I were Starwood—I would think twice about how this hotel is run and sold. As a former front desk agent myself who had to deal with guests complaining about one of our three swimming pools being occasionally closed for private functions, I can't imagine the grief the W's front desk gets about the pool, nightclub, noise, etc. Really, they should detach the club from the property altogether, and stop advertising the fact that they have a pool. Alternatively, guests should be given unlimited access. I just can't imagine why they're not. I think the management forget that although LA residents may expect not to get into places without waiting in line and then, being at the mercy of a bouncer, people from outside of LA—and especially people from outside the US—will see it for what it is: an utter farce. 
If you know what you're getting into and you get a good deal, I'd stay at the W. But if you're a non-celebrity civilian, I'd stay away. Also, I'd NEVER stay here with kids or extended families. It's highly unsuitable. 
In summary, the W is kind of like Los Angeles itself: a magical playground if you're somebody, but depressing and uncomfortable if you're not. But then it's free to walk around LA; it's a small fortune to stay at the W. Why pay to feel like a nobody? I'd happily stay at other Ws because I love the décor, the beds and the Bliss products in the bathroom, but in future I'll be giving this particular one a miss.
A tip for parking: avoid the $40 a day W parking. There is a large parking lot on the same street about 15 seconds walk from the door that does overnight for $20. Just make sure to buy your ticket earlier in the day as we came back one night after 11pm and there was no attendant. We didn't want to chance parking without a ticket so we had to find somewhere else.