Im originally from the burbs northwest of Detroit and have lived in Chicago for two years now. Safety should be a concern WHEREVER you live, in whatever city (not just chicago) but especially when taking public transportation.
I lived in an "up and coming" neighborhood when i first moved to chicago cuz i wanted to be right off the blue line as well... i paid a premium and my luxury suv was vandalized 3 times in a matter of two months and a girl was raped under the train stop i used all the time!
My solution - i moved and always carried by pepperspray. LOL
My point - It doesnt matter how nice and "upcoming" the area, you need to research first and see what YOU are comfortable with.
I moved from Bucktown/Wickerpark even though its an area that everyone told me to live cuz it is hip- I realized I prefer the Gold Coast cuz its like my home town back in michigan.
Basicly, like my, you're going to have to see what YOU like. Safety is relative and you have to treat every area as if the boogy man could be waiting for you in a dark alley after 9pm... carry pepperspray. LOL
My advice - Get a temporary rental for a month and get familiar with the area and others before signing a lease or buying a place. (look on craigslist - there is temp places available all over the city)
I love where i live now, its in the heart of the city, rooftop pool and views of all of chicago and the red line a block away - AND with a reasonable priced parking garage attached (so i can drive to work if need be).
So take your time, come to chicago and enjoy it while you make your OWN decision on what YOU like.
BEST OF LUCK MY FELLOW MICHIGANDER ;-)