Larry,
Your decision is ultimately going to be up to you. You're going to get guys on this forum who will tell you not to get the new E-Trac, either because it's so new(not proven out in the field yet), or who will say all the extra features they see on this new machine won't bring you more depth/target separation, just more confusion. Some folks won't care because they always want the latest/greatest....."Look what I have"...."I certainly will find more than I did before with this new baby". Do you know how many md'ers just bought SE Pros when they first came out? Quite a few. There were even some that traded in their SE's for SE Pros, even though the coil was the only difference.

What's a little worrisome is that this E-Trac is becoming more programmable/(i.e. more complex user interface) with all its settings/software (more so than any previous Explorer model), that it is becoming more like what the DFX has become....to master the machine, you're going to have to know how to properly tweak all its settings to get the most out of it. Some might find that challenging/beneficial, while others will find it very confusing/disadvantageous. I'm sure a lot of the Sov. GT owners will shun this highly programmable machine because all they wanted in the first place was great depth and simplicity which the GT successfully provided. To Minelab, it makes good business sense. Now they can continue to sell you software updates to make more profits.
If you're the type of guy that likes an intricate user interface, and loves to play with lots of programmable settings, then you might enjoy the challenge that this new E-Trac will bring. Plus, you might have to re-learn certain features that you're so used to now with your current Explorer. For instance, one thing I noticed after reading the E-Trac user's manual last night is that its Smartfind screen now has Ferrous on the vertical axis(used to be horizontal axis), and Conductive on the horizontal axis(used to be vertical). This will be a little confusing for existing Explorer users that reference their Smartfind displays for target ID.
It's your call, buddy!! For me, the only way I would consider purchasing this machine is that it would have to outperform my existing SE....I would need to run side-by-side real field tests with both units at various sites/ground conditions/external noise, etc. on deep/iffy targets to find out if one is any better than the other. I will not upgrade because of the new elaborate software interface...and I'm a software engineer too.
Good luck!
CAPTN SE
Dan