I'm full-time now, but only about 3 months on HRT, and no legal name change yet (I just submitted my application this past week). At work, everyone calls me Colleen, and my ID badge, cubicle nameplate, and email address all reflect that, but anything connected to Payroll or HR carries my legal name. The only time THAT'S been a problem was when I needed a password reset, and the dink on the phone kept misunderstanding what I needed, and it turned into a half-hour phone call during which I had to endure endless 'Sir's. After that, I felt like crying. But mostly it's not a problem.
In the meantime, I've (re-)introduced myself to most of my health-care professionals (GP, Dentist, cardiologist, etc.), and I've even sold and bought a house. Each time I need to deal with a person (such as a real-estate agent, lawyer, etc.) who needs to know my legal name, I just explain the situation in a forthright manner, and everyone so far has treated me with the utmost respect. I've bought things in stores with my credit card (which has my old name), and no problem, not even curious looks. Once in a while, I get a double-take, like when I went for bloodwork, and the form had my old name on it, and the nurse came over to the cubicle where I was, sat down, looked at the form, and thought she'd got the wrong form. Almost went back to see what the mixup was. I enjoy times like that - it lets me know I'm PASSING.
But no, I haven't had any problems at all with it. The house purchase closes on July 29, I'm hoping the name change is official before then so I can get the deed in the right name...