Have you guys seen these blogs from dynaTrace before? They give some pretty good explanations, observations and recommendations on really common low level operations and performance issues in regards to SharePoint. Some examples:
SharePoint: Monitoring individual List usage and performance
SharePoint: Performance Problem with LookupField Control
SharePoint: Identifying memory problems introduced by custom code
SharePoint: More on column index and their performance impact
The SharePoint Swiss Army Knife 
Hi Henry
Nice to see that you find my blogs about SharePoint useful. Looking at your site I can see that you have been working with SharePoint for a while.
Would be great to discuss a bit more about things that we both have seen with SharePoint.
While there are many performance issues in SharePoint, there aren’t many appropriate solutions available.
One thing i just discovered is that caching can increase the SharePoint performance dramatically. It just read about a caching software called NCachePoint on http://www.cmswire.com and also looked it up on its manufacturer’s website to find out more. NCachePoint not only caches BLOBs but also caches Views, Lists, Sessions and uses other content optimization techniques to improve SharePoint performance.
NCachePoint has a free edition, i am yet to download it. You can also look at it, maybe this is what you need for your SharePoint performance issues.
i knew another sharepoint performance software called storagepoint, glad to see more and more companies are developing caching solutions for sharepoint.
i’ve also looked at feature list of ncachepoint on alachisoft.com, it looks like great piece of software. it resolves performance and scalability issues of sharepoint with various caching techniques. i think this product is worth considering and buying for heavy sharepoint users or those already facing performance issues due to large number of users accessing data from sharepoint