I'm a big fan of it. I had a DE day a long with an ME day for several months and will definitely go back to it.
Kenny has explained the benefits of training speed a few times and explains it much better than me so i'll let him chime in on that side if he sees this.
From a more practical stand point, people just don't know how to "explode" with a weight. Sure, once you explain, they know what it means to explode/lift fast but they normally still can't do it. It's really interesting. Most of the time when I explain it, i'll need to get on the bench my self a few times and blast it off my chest to show them how fast it should be. The issue is, when you've previously believed "conventional wisdom", it becomes instinctively wrong to lift that fast. We are always taught to lift slow until we begin to know better.
In terms of it being "easy" - if benching is ever easy, you're probably not setting up properly. The bar a lone should be enough to get your heart rate up and a sweat going, if you're getting as tight as you're capable of, which you should. It shouldn't feel nice and it shouldn't feel comfortable. As I find myself saying quite a lot these days - you're lifting heavy sh*t, not taking a warm bath, you're not supposed to be comfortable!
You need to approach every set almost like it's a PB. It's easy to get lazy with this because it's hard work even setting up for a PB and getting your head right for it. This is how you need to approach your speed work. You blast the weight off your chest like your life depends on it. I tell people to "throw the bar through the ceiling". You should hear the the discs clink at the top of the rep.
A good tip I picked up is that each rep should be over before you can finish saying "one thousand one". It's not very scientific but it's a good general guideline, and i'll say this to myself when people are doing a speed set, and my training partner(s) will do the same with me. When the bar speed becomes slow, it's no longer speed work.
Speed work will also call you out on form. If your loose anywhere in your body, you'll be all over the place. It's a great chance to hone your technique and also expose your biggest flaws.
A good way to start this, in terms of progression and just getting to know speed work, is to start with 50% of your max and add 5% (whatever) every week for 4 weeks. In theory, 4 weeks later you should be lifting 70% of your max with a similar bar speed as you were lifting 50% of your max. This is where the magic happens, really. It's just tough to quantify. It becomes very instinctive. When you are new to it, the 5% jumps actually work as a lot of the initial improvement come from gaining the ability to "explode" optimally and 70% really won't look much different from 50% at the end of the cycle. As time goes on I would recommend smaller jumps.
This will also allow you to get very in tune with bar speed and you'll get a feel for how you will perform on heavier days just by the bar speed of the warm up sets. It helps you get to know yourself, really.
Also - If you don't have a speed day, your warm up sets should be treated like speed work.
Also, according to some of their articles, at Westside they will work up to a heavy single AFTER the speed sets, every third workout although i'm sure it varies. I know Cressey tends to work in some heavy stuff after the speed work every 2nd or 3rd week or so.
If you're doing 8-10 sets at ~50%, set 2-5 will most likely show the fastest reps (atleast, in my experience, plus it makes sense). Your aiming to get them as fast as possible. Short rest, too. Generally, after about 6 sets, you will feel (and see) a noticeable decline in bar speed. This is actually what you're aiming for - to fatigue those fast twitch muscle fibres. It's not like getting a pump or burn or failing mid-grind. When the bar speed slows, you've done the job. This is where you see different coaches "principles" all tie in together i.e. westside, thibs, waterbury, etc.