I think you'll have fun with your new MF camera. I recently picked up a cheap TLR, of quality I am sure much below your Mamiya (mine is a somewhat world-weary Weltaflex that says "Made in Germany/USSR OCCUPIED" on the side), and I have been having a lot of fun with it. I have been shooting almost nothing but Ilford FP4 (and this is not an endorsement of recommendation) which I picked because my local camera shop stocks a lot of it, they process it, they're used to processing it, and I have been liking what I have been getting from it. I decided to not noodle around too much for the same reason that others have already mentioned - I want to get to know this film.
One thing I really like about medium format is the depth of quality of the images that I have been seeing. I also shoot a Pentax Spotmatic, and while the Takumar lenses are, in my opinion, superior to the lens on my TLR, I have noticed a certain quality to the images that I do shoot, and I am thinking that some of it may be due to the much larger negative, something on the order of approximately 4 times the size.
I don't really think so much in film vs. digital terms. I have a digital I use, also. It comes in handy to take a picture of the kids doing something funny and send it to my mother-in-law via email quickly. I also sometimes use it to check an exposure just to see if I am even in the right ballpark, keeping in mind that it's CCD and the film in my 35mm SLR or my MF TLR will act a little differently, but to me it's all photography and the most important bit is the eye of the photograher and the care taken in choosing and executing the shot, not in all the gear.
I would like to get a much better MF camera some day, but right now this is about what the finances will bear, and so I am going to have fun with it for now and see what I get.
Adam