Update on current experience using MLO on OSX 10.10 under Wine on a MacBook Air (early 2015). Using the instructions in the forum as far back as 2010, I have MLO 4.3.3 running under both CrossOver and WineSkin. I've finally settled on WineSkin as my preferred choice.
MLO works fine under CrossOver 14.1.6. I had to add IE7 to the bottle. All works fine including cloud sync. My only gripe is that display fonts are not quite right, with the kerning being too tight and making the text hard to read. Tried many combinations of Display DPI and fonts and finally settled on one which made it readable, but was not great.
My preference is WineSkin Winery 2.6.0 with WS9Wine1.7.51. Added msxml3 and msxml4 and IE7 using WineTricks from the Advanced/Utils dialog. Fonts and readability are fine out of the box. Just increased the default font size in MLO/Options from the default. CloudSync is a little slow, but works fine. WineSkin is not quite as slick as CrossOver in that there are several processes running in the background with aggregations of MLO and Wine in their titles, but for saving £40 its a minor irritation.