I went through PDX last weekend on business, and turned my trip into a mileage run to take advantage of the American/Alaska bonus miles. My return trip was PDX-SEA-PDX-SJC, the first two legs on Horizon and the last leg on Alaska. The gate agent was having difficulty getting the baggage tags to print up properly with that routing. I asked if I could simply Check my bags for the final PDX-SJC leg on Alaska. The gate agent said, "I should have thought of that!" and proceeded to do so. She did mentioned in passing that if she were to be a stickler about the rules that I would have to go to the Alaska gate, but that it really wasn't any problem for her to take my bag over to the Alaska baggage belt. Overall, she was very pleasant and helpful.