You can run them together, but you need to make sure that Tribal Fusion knows not to run any contextual ad banners on your site. (I don't know if Tribal Fusion is still running such campaigns these days, but ad networks often do, and TF has done so in the past.)

The problem with cpm campaigns is that the ads are limited to a certain number of displays per visitor. If you have a low number of visitors going through a lot of your pages, the returns with this type of campaign are going to be low. The more unique visitors your site(s) attract, the more revenue you'll earn. I had TF for a while and they paid ok but two things I didn't appreciate: they showed a large percentage of ads for their service (which paid ok but it was not targeted at all to my site); and they stopped displaying ads after 4 unique visitor page views, so you have to have a backup ad campaign. If you have a lot of unique visitor traffic, cpm campaigns should perform well for you. In my case, Adsense outperformed TF by over 10x.

Donster - you must be getting an ecpm of $12 with adsense-congrats.

TF is a good cpm company-one of the best. You will need to set up a default campaign and unfortunately TF has one of the most confusing defaults system I have ever seen. The good news though is that if you can get into TF then you are likely to get into one of the other good 2nd tier companies (actually you will probably need t sign up for more than one). PM me if you want some suggestions

Yes TF is better than Valueclick but it's way harder to get accepted at TF, you will need to have a good quality website that receives a lot of traffic.

TF fill rates is not very good but they do have one one the highest CPM rates and as blairsp mentioned you can run default campaign as as well.

Running TF and Adsense on the same page is fine, you shouldnt worry about that :)