I did find the a Flying review of the TB20 here Review from 1999by Robert Goyer from 1999 but couldn't find anything negative in it.
As I said in post #06, the one by Goyer was favourable. But Flying Magazine did at least two more reviews of the TB20 of which one was done by Dick Collins. The one by Collins is the one that talks about rocking.
Anyway my point is that Flying archives are on the web. No reason to keep them stacked in the attic.
The reviews online is only a fraction of the reviews Flying has published on paper. The reason I threw mine away is that forums like this one make it possible to get directly in touch with the owners and users, which I find it much more useful.
You can but in reality most don't
That will always be true 
The Sandel setup doesn't have its own battery backup, does it?
No, and it wouldn't make sense, because the various signal sources (GPS, NAV, etc) are not battery backed.
If one was doing this properly, one would have 2 alternators, 2 batteries, and a crossbar switch. Like a 737, or the Cessna 400. It's actually a very simple system and I don't know why - apart from the weight of the 2nd battery - why it is not common. Any important items (like the transponder) are powered from both buses via diodes. On the TB20, the TXP is fed from 2 buses (via diodes) which is OK if you are just going around pulling one of the 3 bus CBs, one at a time, but it means nothing otherwise.
No, and it wouldn't make sense, because the various signal sources (GPS, NAV, etc) are not battery backed.
The Aspen has 30 minutes of internal battery backup and an internal emergency GPS. That's a killer feature IMO and often overlooked. The G500 goes dark immediately. I know this feature very well and have used it several times -- because my avionics master switch is positioned so that I regularly turn it off with me knee. Not for much longer though...
BeechFlyer - I see your friend with the Beech Travelair got some feedback on the Socata group from the usual half a dozen people
It still does suprise me however how much more fuel people in the USA are burning for only an ever so slightly higher speed.
I told you. It's not me. It's a friend of mine. 
Seems to be a very nice group though. The offer for the avioniks upgrade was 43k USD. WIth today's prices on twins I think I need to so something now or live with my current baby forever. Because the "investment" would be sunk cost.
Avionics upgrades are usually lost money, in terms of resale value.
It's a bit like putting gold plated taps in a council house bathroom.
The cases where the loss is lower is where the plane is nearly new (which in GA terms means perhaps under 10 years old) and is in excellent condition. Then the price will track the original cost and the upgrade cost more closely.
For example, if you see two TB20GTs, both 2002, and both looked after, both with say 800hrs since new, neither having serious question marks etc, both "zero VAT", and the 2nd one has TCAS (€14k) then the first one might go for €150k and the second one might go for €160k. If the second one has full TKS (€40k?) it might go for €180k.
I know of one TB20GT which was sold maybe 2 years ago, which had every possible option including full TKS, and it sold for something like €200k.
I am not suggesting your plane is a council house but you get the idea. Most GA hardware is really very old, and the value has become decoupled from the original cost plus the cost of upgrades, many years ago. Many piston twins, for example, are worth only the remaining engine TBO.
If you plan major upgrades on say a 30 year old plane, you need to plan on keeping the plane for a long time.
Whenever I think about replacing my TB20 (1999, new engine, full TKS, GNS530) I remember how stable and easy she is to fly and how I went through few challenging situations without any seriuos problem.
Yes; the TB20 is very very hard to replace.
You really have to go to something like a PA46 Jetprop, and then you will lose the "little local flight" capability and pick up an operating cost increment of perhaps 2x to 3x... Not to mention the c. $1M purchase cost.
But I feel that almost nothing will be as strong structurally as a TB20 if one was to get into something really nasty. The PA46 in particular has seen loads of in-flight breakups.
The fact that it no longer exists is the ultimate proof that it can be replaced. It was replaced by the Cirrus, just like all other high performance singles (with the exception of the Bonanza for a few grand dads).
Actually, the Bonanza was pretty much replaced too. They are not selling a lot of them these days although that probably also has something to do with the financial state of Hawker Beechcraft.
Anyway, I appreciate that Cirrus has gotten everything right. The numbers speak for themselves. However, I would not buy one. I want to set the rpm myself, I want manual trim, I also do not want the pedals to move when I move the ailerons, and lastly, I don’t like the spring system in the side stick.
But I guess most pilots see it differently.
