Owlie, I feel like I'm not qualified to respond since mostly everyone has more experience than I. I do find your question raises a tough dilemma because I myself love CX bikes but I think you have to examine closely what you are searching for in your next bike. Although a CX is the one bike that can cross over the lines on both ends of road and trails, seems like if you really are hankering for a new nicer road bike (which I get a strong sense is the case from your posts), the CX would not satisfy this desire since it's going to feel slower and less responsive in steering if you use it for road too. Do you plan on riding fire roads, singletrack; and if so, do you think you'll do it often? A CX bike will work for singletrack but it's going to be tough working uphill and I'm sure even more so coming down. I have a mountain bike and a road myself. Have you test rode the CX bike yet on roads? Are you concerned with gaining speed when you're on a road bike? If so, you most likely will feel the difference between the CX and road. Especially climbing!

CXs are great middle ground bikes but it won't satisfy your desire for a nice road bike. If you are still going to primarily bike on road and want a new road bike, I suspect you'll find the CX bike might not satisfy you when you are on road. It really comes down to trying to predict how much more light trail riding you will adopt. You're basically going to be compromising either way since when you ride on gravel/dirt trails on a road, it'll be suboptimal/ downright uncomfortable ride; conversely when you ride on road with a CX it will be suboptimal. If you decide to ride increasingly "gravelier" trails, then you won't want to take a road at all. In that respect alone, you're prob better off with CX over new road bike. If you didn't want a new road bike so badly, I'd say a CX is always nice to have. If weight is not a concern, go CX. Hmm, tough decision since you're not sure if you'll want to ride trails much.