It's not impossible, but unfortunately it's generally a bit of a fuss to try a switch before you buy it. I live in a major US metropolis (Boston), literally blocks away from the nerd Mecca of MIT, and it was impossible for me to find a brown swith to try to save my life (Microcenter, Best Buy, etc.—nobody had any), or even to see a single Filco board in person. So I just bit the bullet and bought a brown board from Keyboard Co directly in the UK and a blue and red board from Keyboard Co via Amazon marketplace (making returns possible). I figured returning the brown board to the UK if I didn't like it would be either annoying or impossible, so I just planned on giving it away or eBaying it if I didn't like it. I decided to keep the red and brown boards (both of which I love) and sent the blue one (too noisy) back to Amazon. There was a slight restocking fee, but that was no big deal.
I had purchased the test switches from WASD, but that really wasn't good enough to get the true feel of a full board of keys.
I am currently going through this same dilemma as I investigate Topre switches. I want to try out the 30g weight ones, but in this case it's going to require an even bigger leap of faith: plopping down $600 to buy one from an agent via Taobao in China. I'm confident I'll be able to sell it somewhere (eBay, GH, etc) if I don't like it, but unfortunately it requires a big cash outlay just to put your hands on one of these things and figure out if you like it. =\