Yeah, I use a notebook when out, but enter everything into eBird.org afterwards for tracking. Great thing about eBird is I feel like I benefit from other people's sightings. The maps and graphs not only show me where particular species are usually found, but their relative abundance throughout the migration cycles. Helps me plan ahead.
Tell us some of the things you like about Bird Watcher Professional: what kind of data sorting can you do? Any bulk import features (ex. from excel spreadsheet)?