If you care more about gameplay rather than the final look of your minis, than you can't go wrong. If you prefer quality painted minis, I wouldn't solely use speedpaints, if at all. They look best on highly detailed models, final results also vary based on what you primed the models with (smooth, coarse or glossy primers). I've found that the work better as advanced washes/shades over metallics and few other specific uses(sand golem over silver metallics results in a rich gold and shades the recesses at the sametime). I would recommend trying the starter set or a few individual colours first. I also wouldn't recommend these for beginners as they are rather unforgiving and require a decent level of brush accuracy. Painting over them to fix bleeding or brush mistakes often requires multiple coasts (due to reactivation). Because of the re-activation the models almost always require spray varnishing to protect from tabletop handling and especially if you plan to do further highlighting or shading after the speedpaints. Some standout colours IMHO are: Darkwood, Hardened Leather, Sand Golem(gold wash/shade), Gravelord Grey (wash/shade for metallics), Grim Black, Crusader Skin (as a skin wash/shade). The reds are nice, as are most of the greens and I am yet to try any of the blues.
