I have the Zen Theme installed. I have not used desktop Manager for over a year because I have Outlook exchange account so I have not needed it, I thought.

Is there away to downlaod the 4.2 version ota, or is there no point with out using desktop manager. Also has anyone else forgone Desktop Manager?

No. BlackBerry devices cannot be updated OTA.

DM is still useful for the App Loader, backup utility and Media Manager (though I prefer using Mass Storage Mode instead). I wouldn't drop it entirely since it's your only option for OS upgrades.