Closures - My Perspective  
There is a tortuous thread on StarForum (now with over 2,000 posts) that contains some of the strangest logic and assertions I've seen in a long time.  I won't post a link, it really is akin to a religious argument where reason and logic are no match for blind faith and could raise your blood pressure and/or cause neck problems from excessive head-shaking if you read it.  One of the major cork protagonists is David Bryant, of Hillcrest winery in the Yarra Valley.  Despite the fact that they have a no-questions-asked rock-solid replacement policy on corked wines, the material he has posted in this thread has been enough for me to unsubscribe from his mailing list.

FWIW, this is where I stand in the closure debate.

My Requirements.

I buy wines mostly to cellar for between 5 and 15 years, with the aim to be drinking good wines at around 8-10 years of age, with a proportion being held for more time if they need it.  I drink mostly Australian wines, with a (gradually increasing) small percentage of imports.  I want a closure that will deliver consistent results for all/most wines over that period, with a failure rate of less than 1%.

My experience with Cork

I don't keep as detailed a record as TORB, but since we drink a lot of the same/similar wines (excluding tasting samples), my cork failure rate would be fairly similar, around 6-7%, mostly Australian wines.  This includes tca, cork mustiness and prematurely oxidised wines only.  I have seen numerous examples of wines under cork where there is significant bottle-variation within the same case.  I generally seek replacement or refund for cork-tainted wines over $20 and for examples of random oxidation, including older bottles, but it can be a very tedious process at times. It is the mildly tainted, "stripped" wines that are the most annoying, you can't always be sure it is tca and it's hard to describe the fault to secure a replacement.

My experience with Screwcap and Diam

I have never seen a tca-tainted wine under screwcap or Diam in well over 1,000 bottles sealed with these closures.  I have seen a few badly reductive wines under screwcap (winemaking fault) and I have seen a handful of wines under screwcap where there was a fault in a single bottle that made the wine unpleasant drinking compared to the next bottle opened.  I have never noticed any "binder taint" in wines sealed with Diam, including a fair number of sparkling whites and Champagnes.  I have seen a couple of badly oxidised young wines under Diam.

Wine Styles and Winemaking techniques

I understand enough about various winemaking techniques and wine styles to believe some of the winemakers who say their style of wine/winemaking is not suited to the lesser oxygen ingress typical of screwcaps and possibly Diam.  These seem to be mostly full-bodied Shiraz and GSM blends of various types.

Ageing under Screwcap

There is a fair body of evidence, particularly with white wine from the 70's experiments with screwcap and more recently from AWRI and Penfolds that support the view that wines under screwcap age similarly to the best corks.  I'm convinced that screwcaps will give me the most consistent result for many wines that I buy for 10-12 years cellaring and probably more.  See here for information from Fosters, particularly a trial of 1996 Bin 389 Cabernet Shiraz under cork and screwcap, with results 10 years on.

My Conclusions

There is no perfect closure currently available for all wines.

Screwcap has a much smaller failure rate for the sort of wines I buy to cellar and where possible I will buy wines sealed with screwcap.

I am happy to buy wines sealed with Diam and prefer them to cork-sealed wines.

I still buy cork-sealed wines where the wine is desirable enough to be worth the effort to seek replacement of any faulty bottles, but I actively seek alternatives.