In reply to Wilbur:
It depends in a way on how you will be doing it. The walk in can be very boggy, so I'd maybe take some sealskinz socks and another pair of normal socks if you were just wearing tennies as you will get plastered on the approach and way out to the Sligachan. Can be a bit crap having soaking wet shoes caked in mud with soaking wet socks, especially as tennies have very limited shockabsorbancy for a long day so you want your feet to be as good nick as possible.
If however you are taking two days, or someone is picking up your bivvi gear from the start of the ridge, then use the tennies for the ridge, and have some waders for the approach! Having said that I've done long link ups scrambling in N wales and skye with just tennies, and found the weight difference was a real benefit at the end of the day. I'd maybe try a long ten hour day scrambling and climbing in snowdonia to test out how your feet feel in them, and indeed your ankles as they will take a bit of a bashing from the rock, and will need to be strong as you wont have much ankle support.
I'm off to skye this summer, and will be taking my tennies, but with some glue to stick them back together after they fall apart again
chiz