When i first decided on 5 string, i found it a fairly easy transition, the only thing was then relying on the bottom 'B' as a thumb rest 'till i needed it ( a habit a lot of bass players seem to have or so i've noticed ) until you get used to the expanded 'vocabulary' of 5 strings.
I suppose a lot depends on if you think about 'top to bottom string' or vice versa, if that makes sense?
The only problem i have now is doing a gig entirely on a four string these days, i get lost without that low string