I use Postsharp and I like it. It save's me a lot of duplicated code I had to add otherwise.
I did not need any advanced features for log4Net and google is enough to find out how it works. It just does the job. I haven't seen any disadvantages so far.
For Postsharp, the getting started guide on the website, the blog and browsing through the source is enough. A major disadvantage is the increased build time. I hate waiting for my computer to do work. It takes about 8 seconds to press ctrl-shift-b in visual studio (on a fast PC) for the +-60K loc solution with 2 projects using the postsharp build action. If you can, try to use Postsharp in the least amount of projects possible.
When you really don't want to use postsharp, you can create a solution with 20 projects and add the post-build command to every one of them. The build time will be long enough to annoy the rest of the team.
Personally I will probably keep on using Postsharp for future projects. The advantages overrule the extra build time.
