The Web is in a constant state of flux - change is the norm. This doesn't fool anyone, and can backfire if you don't keep the update box up to date. Subscribers enjoy feeling like they are the first to find something new about your list. Incremental change satisfies your regular visitors' need for new features and content. You can solve the bugs in new features with a proactive approach.
Bugs are easier to fix and control on a small scale as opposed to community-wide.
It goes without saying that incremental change is easier to plan and manage on your end. Less pressure, less hassle, and better design demand less resources from you in terms of time and expertise when broken down into smaller steps. You can integrate elements of the very latest in technology and news in your niche by changing your list a piece at a time. You can also integrate user feedback as you go. This will help save you from the dated technology aspects of community site design and keep you attuned to your subscribers' needs.