We've been to Europe 15 times in the past 20 years on mostly-timeshare trips, usually 2-3 weeks of TS and sometimes 4. They have been fabulous beyond belief, that many "trips of a lifetime" so I disagree that timesharing can't work for Europe - but usually I plan much farther out than a few months, often almost 2 years. But I have seen some last-minute gems too. Cities, countryside, ocean, mountains, sometimes close enough to a major city for a couple of days into the city and then other days for further-out exploration. Accommodations have been good to excellent, with only the occasional average to subpar.
Most have been RCI, so maybe II can't offer as many choices. (I did have an upcoming exchange thru II -- then lo and behold RCI suddenly affiliated w/same resort and a larger unit appeared for my exact dates so I took that and ePlussed my II week for something else.) Just to say, it has worked really well with patience and planning.