I think it depends on the iPhone version as well as if you have any anti-glare screen protectors or what case you have on the phone, if any. Using a 4S with the lifeproof case and no screen protector (aside from the glossy front on the Lifeproof), it's usable to me in nearly all lighting conditions. Glare does get in the way from time to time, which makes me wish I could find a polarized visor. I don't like wearing glasses underneath my helmet, so for the moment stick with tinted visors during the day. Anyway, one thing to keep in mind is that while you can save a Google Map as a KML file, you can't really directly import it into Basecamp. Basecamp does support KML files, but support is kinda limited. If I have a saved Google Map I first save to KML, load the KML file in Tyre and preview/alter the waypoints as needed, then save as a GPX file. This resulting file will import directly into Basecamp as a route (via the waypoints) and as a track (the actual Google Maps line), plus all the waypoints. I usually delete the track for on-road riding and rely on the GPS unit to calculate the route using the route portion of the file. You'll probably need to do some tweaking on more complex routes unless you convert the track to a route. Google's route calculation can vary GREATLY from Basecamp's route calculation, which can vary from your GPS's calculation. If you need as much accuracy as you can get, again either convert the track or preview the route in your intended GPS unit before the trip.