I've been running my campaign with DMG for the better part of a year and I love it. Not only has it sped up our sessions, but, it has helped me become a better DM. I'm generally not one to pay attention to every little detail, but, with DMG alot of those details are factored in for me. This is especially true during combat when there is so much going on (not to mention 'heroic' actions by the PCs

) it is often easy to forget something. But DMG does a good job of allowing me to select pre-defined conditions or quickly define my own, and then forget about them (kinda) until they expire.
Another really nice feature is the feat editor. Basically, this editor is an IDE (integrated development environment) for VBScript. DMG comes with numerous pre-defined feats from the SRD and provides support for customizing these feats or creating new ones. Along these lines there is also a Template editor, Race editor, Class editor, Condition editor, weapon editor, item editor... well, you get the idea.
And for DM's who also want to keep their notes in e-form, DMG comes with a robust Campaign Manager. This manager has the mandatory text editor (not another 'editor'...lol) but also allows the DM to create creature groups associated to each entry in the campaign. This makes scripted encounters a breeze to initiate. The Campaign Manager also allows a DM to link an image file to the campaign, so you can have all of your maps, npc pics, etc at your fingertips. You can then place counters representing the party, opponents, loot, or location on the map (and don't forget to check out 'hotspots').
Well, that is enough rambling for now. I highly recommend DMG and Player Genie (4 of 5 players polled at my table use PG). A very stong app with outstanding support from the designer (who frequents the boards and puts out regular updates) and members trolling the DMG forums.