It will be easier in the cooler months - my SIL's baby had one on all summer and it was a PITA, but it looked worse than it was, really, and it hasn't affected the baby's mobility too much, so she won't have lost out on too much time.
If you are still BFing, you can call the ABA counsellors and there is a couple who can talk to you about BFing positions while the harness is on. I know this because my SIL had to seek this same advice!