I don't have much experience with trilogy ... I tested it a year or so ago, but that was the limit of my experience.
I do have all of the Jam packs. They are typically well produced, at 44.1 kHz 16-bit. I would recommend them, but also caution that with a product like the jam packs, everbody has them, so you're not getting anything unique. I love listening to the jam pack sounds in TV commercials these days ... in fact, there's an "oil of olay" commercial that directly lifted some of the jam pack loops I used in "The Apple Pro Training Series: Logic Pro 6" book ...
At the risk of self-promoting, if you want more unique loops, go to our sister site:
[b]The main benefit of the Jam packs are the extra sample-based instruments you get[/b] ... for example, your instrument presets for all of the garageband instruments will increase every time you instal a jam pack ... in the case of the "drum Kits" instrument, this is REALLY useful ... probably worth the price of the jam pack alone.