If you're getting bitterness, you may be overextracting (perhaps due to grind), extracting at too high a temperature, and/or the beans may be stale. If you're just getting started, my recommendation for a good, forgiving coffee is the Intelligentsia Black Cat. With the way they roast/ship upon receiving your order, you're practically assured the freshness will be optimal by the time you receive them. You might get a couple of pounds for practice -- as long as you approach the process like wine tasting, and don't scarf down every shot you pull!
The best thing, of course, is finding a roaster you like in your area, who does good work, has a blend you like, and where you'll know when the batch you're buying was roasted. Or doing it yourself, although that's a learning process all it itself.
One of the things I was able to confirm after I'd suspected is how temperature-stable and predictible the Vetrano is. Wishing to hone my technique as finely as possible, I ordered a Scace device and digital thermometer, but because the Scace was severely backordered, I didn't get it until I had already found the process that works for me. When I was finally able to do some measurements, I found that I was consistently able to get a good temperature curve reliably with what I was doing. Dan Kehn and others have posted on how they use their Vetranos, and I found a lot of good info there. The real lesson is to use your taste buds to fine-tune technique, after you understand what your visual and sensory observations mean.
Have fun!
Note to Luca: I really like the Mini-E, though sometimes I wish it had a worm screw adjustment. Still, no complaints.
