Final verdict on Shimano Ultegra Di2 6770 upgrade ?

My Ultegra Di2 6770 upgrade adventure started because of degradation in the shifting performance of the Ultegra 6700 RD on my 2 year old Lapierre Sensium 300. I replaced the cables and housing once using Shimano SIS 41 cables and housing. Rather embarrassingly I discovered the replacement set of housing to be in rather poor shape.

Maybe my eyesight really is failing but I did not notice how bad the condition had become until I flexed the cables and saw signs of rust. I have never experienced anything like this on mountain bikes or with older Shimano equipment. I have a set of Tiagra 4500 brifters on an older commuter bike. I have replaced the cables and lubricate them occasionally but the cable housing has lasted for years. The cable routing for the Tiagra brifters is quite different and does not require any sharp bends. 

As the cable and housing originates from the side of the brifter, the cable routing is not concealed under bar tape but the housing seems a lot happier and shifting performance seems to require less maintenance over time. Yes, I could have replaced the cables and housing (and been more vigilant about maintenance) but the possibility of going through this again was a real turnoff. 

Even on sale, the Ultegra Di2 6770 upgrade kit is not cheap. The upside:

• More comfortable brake/shift levers, especially if you have smaller hands.
• The travel of the shift is no longer an issue as you are just pushing a button (Shimano seems to recognize this is an issue for some as the Ultegra 6800 brifters require as the Ultegra 6800 brifters require "30% less" travel").
• Once set up, there is no need to tune the RD or FD or worry about cable maintenance. I have not needed to touch anything over the first 1000 km.
• The trimming function of the FD is as good as advertised. The mechanical Ultegra shifters do have trim but this just works so well, even in the chainring / cog combinations that you are 'not supposed to use'.
• The FD really does shift quite happily under torque. I find I don't have anticipate or think ahead when making gear changes. It is nice not to hear the grinding noise coming from the chain and chainring when executing a shift a little too late or early (and thinking about the wear you are putting on your components).
• Being able to shift easily when off the saddle is actually really nice for climbing.
• I am not a weight weenie but being a smaller and lighter rider, I am not completely immune to weight concerns either. If  you are wavering between something like the Ultegra 6700 and Ultegra 6770 Di2, the weight difference is not noticeable, at least to me. 
• The RD and FD do make a little noise but with the wind you get when riding, I just don't hear it. 
• The battery seems to last as long as Shimano claims (think the RD stops functioning first to help get you home if you neglect to check the battery)

There really is not much to complain about. The downside:

• At least for this iteration of Di2, there is not really any feedback, either in noise or feel when changing gears and it is true that you  wonder at times if you have changed gears or not. 
• In summer, I have had no problem with mis-shifts. The buttons are offset and you can feel the difference in texture. I don't know if it will be as easy in winter with thick gloves on.
• I have found that changing wheels, even with the same cassette, does sometimes  require a little tweaking but it is done the same way as the original setup and requires no tools.
• The RD or FD will be a lot more expensive when or if they need replacement due to a crash or some other mishap (there is a crash mode that temporarily disables the RD for protection - nice touch).
• I hope I don't have to test the RD with a bent derailleur hanger. I would still hesitate to do any touring with this setup.

Conclusion, if any:

I still feel a little guilty for spending money on components that give some convenience but do nothing to make you go any faster. The concerns about frame compatibility, appearance, weight, ease of installation and use are, in my opinion, not really a problem. I was hoping to read something or be told something either by a fellow rider or a staff member at one of the LBSs that I deal with that would convince me this was a good decision. I enjoy riding my other bikes, all with mechanical groupsets, just as much, but in different ways. If you upgrade your bike to Di2 or buy a new bike with this groupset, I'm sure you will not be disappointed. Ultimately, the decision does come down to personal preference and whether or not you can afford it.