Upgraded my Pearl to 4.5.0.99 last Thursday. Used DesktopManager 4.5. Nice work! Don't have any issues with it. Plus BB browser works through internet.mts.ru APN now, instead of wap.mts.ru in previous OS build (my last was 4.5.0.55). So I can provide more OTA downloads without astronomic bills for data usage!
RIM - You are at the right course!