Dear Jeff, thanks a lot for raising such an interesting and for me very inspiring topic.
The L5100 may have its fair share of aestethic faults but to me it is and will be my favourite calibre, no doubts about it.
So saying that I like it can really be something of understatement ;-P!

It has so many features that make it so special:

- The fact that all my favourite brands (Heuer, Sinn and Omega) have produced outstanding watches with it
- The clarity of the dial layout with the central chrono minute hand
- The military connection
- The ability to withstand 7g-plus accelerations
- The 24-hr subdial
- The fact that no hand 'jumps' but they all move in a continuous fashion
- etc. (I think I could go on very long!)

I've never had any issues at all with any L5100-powered watch. Service can be tricky but the right watchmakers (and we have an ample selection represented here on OtD!) can do that.
As Paul says, as a user I am really not into fancy movements from the technical side and I don't mind plastic - I think Mark is right, plastic is the element of modern life and what (IMHO with electricity) has made progress accelerate so much in the past 100 years.
It is however true that a naked L5100 really looks ugly even to my untrained eye, even more than the V7750: but on the other hand I have never been one for display backs, they just make me laugh on what are supposed to be tool watches.

Which are my favourite L5100's? That's a tricky question because I immensely like all that I own and still lust after the Holy Grail Omega Speedy 376.0822 (but will never be able to afford it at the current price levels!).
If pushed my current favourites list would be - trying to strike a balance among brands as well:
1. Sinn 157 Ti Ty in the titanium case
2. Heuer 510.501 day-date version black PVD
3. Omega Speedmaster 176.0012, probably the earliest L5100 of them all. This one is definitely the most elegant of all I own.

But indeed I really also love the Heuer 510.500, the Sinn 142, the Revue Thommen Airspeed etc. So ask me again in a couple of months and my selection may have changed LOL!
On the other hand I don't like the L5100 Tutimas, PD's, Paul Picots etc. at all.So not all L5100's will do for me. And I never got the EZM1 buzz, though I understand it's considered the ultimate Sinn and maybe also the ultimate L5100 by most collectors.

For what concerns its ability to become a classic over time, I think the answer set that this thread has got more than shows it already is, isn't it?
Cheers,
Fabrizio