I mostly agree with you in that it's usually negative. But, outside the US, I think it's quite different.

It's not as you say that "as opposed to appealing to the elites who would presumably understand that the thing's a bad idea". The elites tend to consider something as a bad idea, when that somethings affects their interests. A populist policy, usually does not benefit the elites, au contraire, it usually affects them negatively, by moving benefits from them to the masses. (Also, in favor of a political gain, like raising the approval ratings).

I'll give you a practical and real example:
here in Argentina, the vast majority of the agricultural production is in hands of about 2000 elite families, and managed by planting pools (they have around 85% of the productive fields, and only 15% is in hands of small farm-owners). One common practice for those elites historically has been to export the production, but making the transaction outside the country, so they wouldn't pay taxes here. And then, leave their gains in foreign banks (Switzerland, Luxembourg, Uruguay). Then, after our crisis in 2001, the government crated a grain exports tax. Around the 2006/2008, soybean prices skyrocketed[1]. The government wanted to modify the tax, so it would have a sliding-scale taxation system, that would make that the more expensive the international price of a product, the less impact would have in the internal price [2]. It had two objectives. The first, was to avoid having exorbitant food prices inside the country, that would make lots of products inaccessible to large segments of the population (mostly meat). And the second one was to allow the government to get more money from the soybean exports (so they could use that money to finance the industrial sector). Even when the agricultural elites would still have the highest benefits of their entire history, they didn't want the government taking part of those. This bill was seen as a populist measure by the agricultural elites, who forced a lockout that lasted more than four months. Mass media and mainly Clarin, the largest media conglomerate of Argentina, who until then was a governments ally, aligned to those elites interests, and started a heavy campaign against the government (marking the beginning of a war that still lasts).

I'm not referring to any specific government here, but the main problem, I think while seeing it from the outside, is that US politics has only two options: Conservative-Right and Liberal-Right. So, when you see a foreign center or center-left government implementing policies like progressive taxation (as in my previous example), mixed economy or the state regulating the economy, your media tends to jump shelling "populist! populist!".
So, even when "populism" is usually used as a pejorative term, it shouldn't be. It should be used for a government who tries to fight for their lower classes against the elites. The term that should be used instead, (and the one you are referring, I believe) is demagogy: "a political leader in a democracy who appeals to the emotions, prejudices, and ignorance of the poorer and less-educated classes in order to gain power" [3].

[1] http://www.indexmundi.com/commodities/?commodity=soybeans...

[2] http://es.wikipedia.org/wiki/Paro_agropecuario_patronal_en_A... (in spanish, sorry)

[3] http://en.wikipedia.org/wiki/Demagogue

PS: I also follow politics a lot, my parents where politically active, but they've always let me choose my own believes.