dGB is very simple, stable and fast. It does not include an a2sd script, which was the main caveat. To get the most from it you need to use a "custom hboot" that will repartition your internal storage - shrinking your /system partition (where the ROM lives) and giving the space you your /data partition (the user's internal storage - user apps and app data). You can also move apps to SD as with the stock ROM to save more space.
The custom hboot is a slightly more "advanced" mod than partitioning the sd card, because the sd card is not vital to the phone but the bootloader is
The download site for dGB also includes the custom hboot for it - 2 versions, 60 and 65. If you think you might make any changes to the system (even theming) then 65 might be better. There will also be md5 checksums for these - it's important to use these to check that you have a good download, because you don't want to flash a corrupted hboot. The "root memory faq" has a section on custom hboots, and you can find instructions for flashing them at alpharev.nl. Read these until you are happy, or ask for more info, because this isn't something you want to get wrong.
Having said all of that, you don't have to do it straight away. You can flash dGB just like any other ROM without using the custom hboot - the only drawback is that you don't get any extra space for apps that way. This is actually what I'd recommend: try the ROM without changing hboot and see whether you like it. If you do, you can then take a recovery backup, flash the custom hboot, then restore the backup, and this will give you the extra space. If you don't like it, you can just try another ROM or revert back to the original one and don't need to worry about custom hboots (yet - if you get into this you'll try them sooner or later
).