[Overdrive]

No expert on this matter, but just thinking logically, since you didn't say anything to the effect of "I grind the gears a lot" or "I'm just learning how to do this", I have to figure you know what you're doing, otherwise you wouldn't be even attempting it. If you're doing it without problems, I'd imagine you'll bring some more wear and tear upon the tranny (to a point) than using the clutch, but not nearly as much as if you were grinding things or using a clutch poorly. It also sounds like it's not something you do constantly, so I don't think you'll have a problem until much later in the life of the car, if at all.