Although the find in Mail is not as robust as something like Outlook, it works very well for what it is. I don't find it cumbersome at all. Yes your right about "no way to sort messages easily by subject, author, etc". Also what client do you use that let's you easily see hundreds of message subjects at once? Or are you comparing a email client to a checking on the browser? Even on Outlook I can't do that with all my mail collapsed. Lion's Mail collapse sucks, it doesn't even collapse anything(at least in the traditional sense).
Lion's Mail compared to previous versions is a huge upgrade!! I can finally use it for my personal email. Previous versions were just to horrible to use for anything. I still use Outlook for my business emails.
Apple's Mail should be as robust and powerful as Outlook or Eudora. There is no reason it has to suck. It can still have the new 'pretty' fluff, but behind the scenes, it should be functional.
Regarding the search feature, to search for something in the subject field, one must use a keystroke to get to the search box, then scroll down a list to search by subject, then find your message in an inadequate (doesn't display enough messages) message viewer. That is cumbersome. Others have pointed out that you can't just search one mailbox at a time, but that you must search all of them. That is both useless and cumbersome.
Apple Address Book used to be pretty good. It's morphed into another 'pretty' useless program that is fine for people with 20 contacts, but cumbersome for 1500 contacts.
This is too bad since Apple certainly has the ability to add power under the hood for these key programs.
They could, especially given there current size and market cap, with a bit of fine tuning, create business friendly applications that would crush Microsoft.
I really wonder what other programs and features have been wrecked in Lion.