I understand the hesitation to finish in the oven but have found myself in need of doing so a few times. This is a point of disagreement between my father and I, who has been smoking longer than I have. However, I think that there are more factors involved than whether or not the oven is used and if it is covered. First, how long it was on the smoke. Second, how much smoke was being used. I keep my butts on the smoke for 4 hours at 275 with a lot of smoke (3 parts apple and 1 part cherry with more woods chunks being added every 30 minutes) and them finish in the oven (covered) at the same temp. I end up with a nice smoke ring and bark and no crock pot taste. So, if you used enough smoke I think will be OK. As evidence for my claims here are pics from the last butt I made. Note: no liquid was added at the oven stage and a probe thermo was used. The pork was like butter.
After 4 hours:
After finishing in the oven and being pulled: