An interesting question posed recently on NAM with a great reply by MINIhune (a NAM moderator) who writes:
Those with modded MINIs (MCS mostly) eventually stop or at least slow down on upgrades when:
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3. You’ve come to your senses and realize that you are now in a group of MINI owners that have spent well over $15K or $20+K worth of mods on a $25K car
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5. You’ve done all that you wanted to do and are very happy with how your MINI drives (but you are getting bored and want to sell it for the newest MINI model because of the new features)
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Read the whole thread (and MINIhunes complete reply) here
UPDATE: A very interesting discussion about the pros & cons of upgrading your engine on MINI2 at the moment – the discussion focuses on the MTH upgrade but is largely applicable to any engine re-programming …
Me? Apart from new (non-runflat) tires coming soon, I have no plans at the moment. But I sometimes wonder how much an ’05 6 speed transmission with LSD would cost 🙂
M&I / GBMINI 
Just a shade over $24k, “comfortably” configured with the premium and sport packages. 🙂
I don’t understand. My MINI must be continuously fed. Even with my previous car, when I thought I did all I wanted, something new came along. Some of us are just too crazy to ever come to our senses. 🙂
NOTE: As well as the MTH pros/cons thread referenced above, there is another MTH problems poll thread which indicates that the problems are minimal and probably no higher than if the same poll was taken with stock MINIs …
That NAM thread’s been locked and/or deleted due to some kind of pissing contest between the NAM and MTH folks. There’s another thread on NAM where NAM folk can discuss, but from which MTH employees are banned.
Crikey! That MINI2 thread’s also been nuked? What is *up* with these people?