I just installed MailDroid on my new Motorola Razr (Verizon) phone and I like it very much. I was specifically looking for a mobile mail client that would allow me to delete messages off my phone while leaving them on the server, and this app works very well in that respect. Neither the default mail app nor the Yahoo app would let me do that, or at least if either would, I couldn't find the option.

A couple of things I'm still trying to figure out: How to set up "rules" efficiently and how to either access or set up folders, particularly a Sent folder.