I've had a Warco WM250V for over 4 years.
For milling, I use a Myford double-swivel vertical slide that I retained from the Speed 10 I had previously. I want to buy a mill and will probably do so eventually, but my plans for this keep getting put back because I'm always finding that I actually can do what's required in the vertical slide. In that situation, the carriage handwheel becomes analogous to the knee in a vertical mill, and although the graduations are 0,25mm or approx 10 thou, you can still be accurate enough to a couple of thou if you use care.
It's very easy to set the slide square to the spindle, by locating the top face of the vice against two chuck jaws before tightening the baseplate down to the crossslide t-slots. I had to modify the Warco adaptor plate to suit the Myford vertical slide, but that wasn't difficult.
I've always questioned the rigidity of column milling attachments. I know my arrangement doesn't permit of greedy cuts in strong materials, but I think it may be better than a column attachment – and it's certainly cheaper.
In the pic, I'm boring a radius in a reinforcing segment for a ring gear. It's a dodgy-looking operation but it worked so long as I kept each cut down to 25 thou or so:-
