Glen Bogle is quite an aquired taste i would think, i have very limited sport climbing experience but here goes. During midge season forget it, they will eat you alive, the main concentration of routes are on the Dark side, do you possess the force? the routes tend to be very short and crimpy and there are some hard classics, Digital quartz 8b and Off the beaten track 8a ***.
The sunnyside ( other side of glen) has a pleasant ambience, with a real spread of grades, i really enjoyed Overkill 7a+ **.
But to cut to the chase, avoid summer at all costs, spring and autumn would be prime time and expect the routes to be a little dirty as they see very little traffic.
