Over the years I've used (and owned) most 90's and most other Leica lenses. I got the 90AA when it came out, was astounded by the image quality at longer distances wide open, but otherwise never really enjoyed the lens like I did the various variations of the non aspheric Summicrons. If I get another one it would be the last iteration before the 90AA.
On the other hand, one of the most despised (relative term) lenses in Leica's history, the skinny Tele-Elmarit, happens to be one that I've taken a large number of pictures with that I really enjoy, even though technically it isn't nearly as good as the later Elmarit or certainly the 90AA. So I still have a decent example of the T-E. I also have the last Elmarit, which comes along when I want something that provides a somewhat crisper image wide open.
My main longer lenses are the 75/2 and 75/1.4, both of which I really like. I don't have either focussing nor framing problems with them on my M8's nor other M cameras, and which one comes along depends on need for speed, weight considerations and especially rendering capabilities. Sometimes I do carry a 135 along for extra reach, but that function, when it's likely to be needed more often, is generally filled by an SLR.
When travelling I usually take the 75/2 because it's the size of the 90 T-E with a bit more weight, but more speed and optical performance that can't be beat, both near and far. It, as well as the Summilux, also focusses to .7m instead of 1m like the 90's giving the smallest field of view outside of the 90/4 macro (too slow for me, but great performance).
As far as reviews go, while I find Sean's site interesting reading his predilections are generally not mine (for example, the viewfinder intrusion issue is not something that I pay much attention to) but his site is interesting and at least it's from an RF user's perspective. KR is just laughable, and not just wrt rangefinders.
In the end it depends of course on your own predilections and which set of lenses you prefer. If I take 3 for general use on the M8, it's the 21/1.4, 35/1.4 and 75 either f/2 or f/1.4. On film it's likely to be the WATE, 28/2, 50/1.4 and 90/2.8 or if it's going to be only outside and it's bright, the WATE, MATE, and 90 T-E.
Henning