I have a slightly different opinion, suggestions and experience. I followed Healthy Sleep Habits Happy Child as he was our pediatrician. He's a very nice, down to earth guy, and very much in line with my own thoughts about sleeping. I did have them cry it out, fairly early on, not hours of course, but especially with my twins (and another 2 yo in the house) I couldn't physically attend all children at the same time.
My general belief (and experience), like Weissbluth, is that overtired children have less problems falling and staying asleep. Many children are going to bed overtired, whether it's at nap time or night time. It's hard to settle when you're really tired, or fall back to sleep once you wake up. My oldest was going to bed at 7 pm around 8 weeks old and would sleep 10 hours straight, then her napping regressed and I put her down at 6 pm at 3 months (his advice) and she slept 13 hours straight, and napping improved slightly as well. My twins went to bed at 6 pm at 8 weeks because I had to take care of my then 2 yo afterwards (who was going to bed at 7 pm at that point). I wasn't in Hong Kong, had no helper and was on my own. So the twins would wake up around midnight at first and then again at around 5 am, go back to sleep til 7 am. At around 2 (3-4 for my son) months, they dropped the midnight one, and the basically slept 11 hours straight. They were fairly good nappers too. Once getting older, I slightly pushed their bed time back, but 5 years later, we're still only a little past 7 pm.
Early bedtimes are not always great as my husband didn't get to see them much but they were very well rested, good sleepers and we all benefit from that. Now years later, I can basically say I never had any major sleep issues, except the rare night mare. They go to bed early (currently between 7-8 pm, they are in Primary), they are well rested. And that's all that matters in the end.
By putting them to bed drowsy but not too tired, they fall asleep more easily. At first there may have been little crying but nothing excessive and within weeks they were soothing themselves to sleep (at 3-4 months). It's like Weissbluth says, you have to choose the right moment. Go too early ... they won't sleep, wait too long, and it will be more of a struggle too. It's not easy, but with practice you will find out what works for your child.
Not saying it's for everybody, but my children were / are perfect examples and it's something else to consider. I do believe you can sleep train early on, and most children could be very good sleepers if we would just offer them enough sleep.