VS2015 with the l&g PTVS looks great.  
But any non-trivial project runs about 20-50 times slower under a debugger (F5) than without one (Ctrl-F5), which makes it totally unusable for debugging.  
Any idea why? Is there any way to accelerate the debugger?
As a workaround, try mixed-mode debugging - it is significantly faster (but also more limited).
Why is PTVS so slow?