If you are referring the infamous 75% tax, it was initially supposed to be a new tax bracket for the income tax (so any source of income above 1 million €), but it has been transformed in a tax paid by companies that are paying salaries and bonus above 1 million €, and it is capped to 5% of company revenue.

From my understanding, it means that for whatever reason you get an income above 1 million € this year for selling a company or renting apartment complex, or any other mean, the 75% tax does not apply to you.

The biggest contributors so far seem to be Football clubs, and likely some financial institutions. I don't have the exact number at hand but it is projected to only raise 200 millions. It concerned about 400 companies and 1000 people. It was only applied for 2013-2014 and seems to be abandoned for 2015.

For the most part, the uber rich are not rich because of their salary. Bill Gates or Steve Job, had they been French, would not have payed the 75% tax.

That does not make the idea less socialist, but I think it is a bit overblown internationally given how few people are impacted.

Considering that Sarkozy was increasing tax pressure by the end of his mandate and would have probably done so again, had he been re-elected, not really. As for the rich, they've been practising tax evasion for a long time. I'm not aware that hordes of rich Frenchmen fled to Switzerland since Hollande got voted in, but I'll be happy to see numbers which prove me wrong.