Hi all! I'm back from a weekend away.
Interesting to see a bit more depth to the conversation. Still lots of different opinions but very little consensus!
It seems that "controlled air space" is some sort of bogeyman and "GPS" is the teddybear that is used for comfort!
Thanks for the discussion, I’ll tie up some loose ends and then I’m out! Happy magenta lines! 
With all due respect, Pilot DAR, you mix up your metaphors.
To me, it's sort of like getting into a Cessna 182RG, and saying well, I'll not bother retracting the wheels, 'cause I never did on the regular 182 I used to fly! Advances are made, we should make good use of them!
To use the same metaphor, I would have said that "I like to fly fixed gear planes from A to B" to which the “professional” pilot crowd would have answered "it's completely ridiculous, you look stupid, it's less efficient and you're not taking advantage of modern advances" and so on. Apart from that, always a pleasure to read your posts.
The rest is quite interesting as well.
421C tells me that:
No GPSs are "installed" without intergrity monitoring. Every TSO'd panel mount has RAIM and most have RAIM with Fault Detection and Exclusion. Every TSO'd panel mount I know of has a database supplied by Jepp or by Garmin from Jepp. Both these hold Type 2 LoAs showing the same conformity to Do200A/ED76 as airline database suppliers
OK. I take your word for it. But, last time I looked, my friend's plane had three GPS "installed" (in case there is a special meaning in the ANO/FAR/JAR etc for "installed"!). One is a Garmin 100 AVD that hasn't had a database update in at least 10 years. The other is something like a Garmin 76, similarly on its original database and the last is a 496, roughly a year old.
GA GPS installations frequently fly to a more demanding level of performance simply because the US now has more WAAS approaches than ILS - this is more demanding than any enroute/terminal RNP application I can think of. In Europe, the most demanding is P-RNAV (RNP1) which, ironically, the GA fleet with its fairly homogenous GNS430/530 kit can conform to more easily than many older airliners with legacy FMS.
Sorry VOD80, what ever your point about GPS is, trying to make out that GA IFR GPS is inadequate is not helping your cause.
Not sure what "my cause" is, but I think that if you're telling me that the triple redundant system I mentioned above is equivalent to a Garmin 530/430 setup, or that any time someone cellotapes a GPS to the yoke that it's the same... I'm slipping into the parallel universe again!
I'm interested in day VFR SEP flying and I've never pretended that the way I fly (day VFR SEP, just in case you forget) could be applied to RNP1 (or RNP0.5/RNP0.3 and such like as are following).
I suspect that the same applies to the Auster pilot identified above (the post seems to have gone now) where he is too cheap to get his altimeter replaced and uses altitude information from his GPS. How much is he likely to spend on keeping his GPS up to date? I don't know what kind of GPS, whether it is GPS altitude or baro altitude but - what an interesting attitude. Kind of makes me want to deny ever having been interested in Austers!
What next indeed, "What Next". I wonder again, if we're talking about the same thing. Your mental model of airspace seems incorrect. There is separation between different types of traffic. Airways are Class A, big airports are Class A, others are Class D and so on. We (day VFR SEP) are not allowed in. We're kept separated from the others. Unless we ask, in which case we may be allowed in. "May", because it is conditional. But, this is irrespective of GPS.
Same thing for your TA/RA story. This has (as far as I can see) nothing to do with GPS and everything to do with "transponder" - it's a bit further down the stack - and you should be happy that your three TA/RA events were between aircraft equiped with such!
Class F is open to VFR pilots. No clearance required. So, if you had TA/RA events in Class F, this is a sign that two sets of "see and avoids" failed (to some extent). Again, unless you show me otherwise, GPS is irrelevant. Also irrelevant that lo-cost airlines flies in Class F airspace. This might be a justification for reclassification of the airspace into Class D, but that is a separate discussion.
Some fundamental misconceptions there.
Just to finish, a little word on efficiency for Chuck. In your haste to come and beat me about the head 
I think you tripped up over the meaning of the word efficiency. Do you mix it up with “imprecise”? Efficiency is just a measure of the conversion of an input into an output. Think "miles per gallon" in car terms.
To be interested in Austers is to be a worshipper at the altar of inefficiency. Mine would carry 190kg 285nm using 110 litres of fuel in 3 hours. I could land with one hour’s fuel in reserve. The C172 I would like to eventually get would the following: 302kg 285nm using 90 litres of fuel over 2.75 hours (again with reserves of 1hour). With some simple figure of merit, that makes the C172 twice as efficient as the Auster.
I deliberately chose the less efficient solution for romantic (and economic, to be honest) reasons.
I used to fly between Toulouse and Gloucester. The great circle distance is 530nm. I used to fly a distance of 630nm. In this case, it was a reluctance to trust my engine over the 70nm channel and a desire to reduce risk of having to learning to swim!
I used to fly at about 3000 feet when I could probably have got better efficiency by going up higher, but I preferred the view lower down. I flight plan for a couple of hours on paper when I could have got more efficiency using a computer for 15 minutes.
And so on and so on. Loads of conscious decisions to be less efficient than I could have been. But, in my opinion, no discernable impact on flight safety (for a day VFR SEP…)