This service is great. I don't think it will affect your adsense much... I don't think it will affect it at all. I have YPN and it hasn't affected me at all. Argothusz it didn't fit with mine either lol I just edited the layouts.
EntreCard has actually been very valuable to my blog, especially considering my blog is fairly new. With EntreCard people actually have to visit your site to "drop" their card, which gives you visitors, unlike BlogRush. Also, because of EntreCard my Alexa has improved and I get more comments. Right now I am one of the top Tech blogs at EntreCard and as long as you participate in the community (going to the forums and making sure to reciprocate drops on sites that drop on you) you will definitely benefit from it. I am not affiliated with EntreCard (even though it sounds like it). I just like the service and what it has done to increase the quality of my readership. Oh, and BlogRush sucked horribly for me.
See! Entrecard does work! I really suggest you guys try it. My alexa ranked has also improved by A LOT.
zman07 that is true. But you can easily prevent it with a simple "please post a comment if you drop my Entrecard" the only thing that Entrecard MAY affect is bounce rate, but I have not seen it go up with my site.