Wanted to add my experience here – I have the A6000 and have been using a Minolta 50mm F2, 50mm F21.4, and 45mm F2 (along w a Minolta 80-200 telephoto). I also recently purchased the Sony SEL50F18 Lens as part of a package deal, and did a comparison…
– First, the manual focus of the legacy lenses isn't something to be scared off by. Put the camera in Aperture priority and experiment a little. I'm still a newbie in photography (only stopped shooting in auto about a year ago), and it's been awesome. With the Sony's (and I think most mirrorless), the focus peaking makes focusing a pretty easy job.
– I inherited the 50mm F2, and it's in excellent condition. The 45mm F2 is about 3/4 the size, and it's in good condition. The 50mm 1.4 has a decent amount of fungus, but I couldn't resist testing it out for $20 on Craigslist (F1.4 for $20!!!).
I did a sharpness comparison, and my copies show this (I only evaluated the center, because I would only really use these for portrait-ish lenses).
– The 50mm F2 is pretty decent at 2.0, but good at 2.8 and sharp at 4.
– The 50mm F1.4 is soft at 1.4, OK at 2.0, decent at 2.8, and sharp at 4
– The sony SEL50F18 is Good at 1.8, and Sharp at 2.0
For my money, I am going to keep the Sony lens for a few weeks (birth of a child), then selling it. The Minolta legacy lenses are absolutely serviceable for my needs, as long as they are modestly stopped down. My copy of the 50mm F2 is totally workable at F2.8, and really isn't bad at 2.0. The 50mmF1.4 isn't great wide open, but it's kind of fund to play with. It may be because of the fungus, but it definitely isn't as sharp as the F2.0 at 2.0.
Hopefully that's helpful!