I do it regularly. Email is easiest, but also easiest for them to ignore. Phone calls, paper letters, and faxes require a minute or two more effort but are much more effective.
As for response, paper letters or faxes with my mailing address attached usually get a form-letter response - “Thank you for contacting me on this issue, here’s my position, blah blah blah.” Emails sometimes get a similar, emailed response.
Phone calls are generally handled by low-level aides. Usually they’ll ask what issue you’re calling about, ask for your zip (to confirm you’re a constituent), and presumably write down what you say. I have in the past gotten a slightly more personalized letter from a representative in response to a phone call, with a sentence thanking me for being an “active participant in the government”, which was cool.
Go for it. The worst that happens is…you spent ten minutes sorting out your position on an issue and get no response. But I’d like to think that they pay at least some attention to feedback from their constituents.
ETA: It’s nice if they’ll try, but your congressional representatives aren’t really there to try to solve problems on a personal level. They’re supposed to represent your voice on the national level. Calling for nation-wide insurance reform, yes. Helping you get a claim approved is a nice bonus if it happens, but it’s not their job.