Myself and 2 others at my flight department fly 3 different types. We use that to our advantage when talking money with the boss. In fact, I always trot out the NBAA Salary Survey and use the "Senior Captain" tables for pay discussions because one of the criteria for Senior Captain is "...flies multiple aircraft..."

It's a 2 edged sword. Getting multiple types is great should one need them for job searches. Also, the variety is cool. But the additional training and the additional trips take a toll, and I feel I should be compensated accordingly.