Surprised there has been no mention of .sdx files for moving data around. Is the .sdx file format going to be supported any longer with the deprecation of the tools that create/consume them?
I agree with bixb0012 about GUI options being a step back for administrators. As your environment grows, automation and anomaly identification become key for monitoring and finding problems. If you want to check things one at a time, GUI is fine but if you want to setup alerts to let you know when a spatial index is missing or sub-optimal GUI is not all that helpful.
Along those lines, haven't heard any response to the si_stats question. I've have problems with GDBT crashing on me a lot in the past so have favored si_stats for spatial index analysis and tuning. let's face it, Windows GUI is slower and much less stable than a simple background thread and doesn't lock up my environment and prevent me from doing other work.
Same point here about GUI vs. command line. If you want to setup a job to check all of your SIs to make sure none have too many features per grid... I don't care what the tool is - SDE command line, python, LOGO, smoke signals... I just don't want to have to sit there and click it all day with my mouse. Much more productive to review a report of anomalies each morning and do analysis and resolution instead of monitoring.