Just tried it here, I normally use Mail.app.<p>First impressions were "oh, this isn't so bad," but then I started using it. It feels very janky, the interface is a bit disfunctional (going to File > New Folder gave absolutely no visual feedback as to where it put it, and if you have the filters window open and make a new folder you have to close and reopen the filters window for it to notice the new folder). The one thing I saw that I liked was the "Reply to Mailing list" button, but that just didn't work, at all. The To: recipient was the person who wrote the email, not the list. Also, I couldn't figure out how to open a new tab.<p>E for Effort I suppose, but it's seeming less and less relevant, and if major releases are this buggy I can see why.