If you can do it and get the traffic there is no better way. For seo it is not that simple and some of the ppc experts here can speak to how that messes with quality scores and editorial issues. But all other factors aside, yes, of course it is best to link directly to the order/sales page!
Let me attempt to clarify what I mean by niche.
Selling a specific brand of cell phones is not niche. Cell phones are a highly sought after product. I have not promoted cell phones and do not know if the CPA is high enough and it does run into the major offline competition however. That said, I am certainly not saying my way is the only way - just ONE WAY that has proven to work.
An example that may be clearer is "Diet Pills". Obviously there is a huge demand for weight loss products. Always has been, always will be. Just because you are selling a secret, special, one of a kind, seen-nowhere-else diet pill, does not make your offering niche (in the way I am using the term). I am talking about spending days finding niches where there are very, very few online buyers in the general category.
Conversion rates need to be at 1.5%-2% on decent traffic. If you are just throwing junk out there, that's an entirely different, and often effective strategy as well. But it may be useful to simply do the math...
Another clarification I should make is I am not talking about making $30-50 a day (if I were I should be shot for posting). I am talking about systematically making $30-50 a day for many programs with little effort AND, most importantly, finding what works and beating it till it is dead, then beating it a few more times :)
Many affiliates spend day upon day thinking about strategies when the single most important factor by far is the program itself - so choose wisely!