I've been playing this weekend, I'm a level 15 "good guy", specializing in science, repair, and small guns (and to a lesser extent big guns and locks), and I only feel like I'm halfway through (I'm taking my time doing every side quest I get before chasing Liam halfway across the wastes.) Caps are useful for upgrading your house and buying building plans. You can easily reach your weight allotment chasing the mats for building plans, but the stuff you can build is AWESOME. Strong Back is the best perk ever.