There's a new option now. (full disclosure: I am the author)
amigaXfer is an
easy to use GUI tool for lightning fast serial-port floppy and file transfers.
All Classic Amiga models are supported. All AmigaOS (1.x/2.x/3.x), all Kickstart versions (I have tested 34/37/39/40/45).
All you need is an Amiga, another computer and a serial cable (any null-modem will work, only 3 wires used).
It does achieve 512kbit/s on a basic A500, no expansions. Most PC serial ports only go up to 115200, but it is possible to get these higher speeds with usb-serial adapters.
As it uses the Kickstart built-in debugger, no software is needed in the Amiga side. Just
loadwb -debug, select the Debug/RomWack/SAD option in Workbench's extra debug menu and enjoy.
I provide Win32 binaries, they should work on Windows 7 or higher.
http://aminet.net/package/comm/misc/amigaXfer_win32
Otherwise, other platforms will work if using the source code. This is Python 3.8+, PySerial and WxPython based.
Open Source, MIT License.