When you have error in SharePoint 2010 you are provided with Correlation ID that identify that error.

SharePoint 2010 Term Store is able to store the following number of items: 

Microsoft released SharePoint 2010 Whitepaper where all software bounds and limitations are described

The following table summarize the options of how how you can use Remote BLOB Storage (RBS)  and Microsoft SQL Server 2008 together with  SharePoint  2010

The following table represent the recommended SQL Server RAM for the SharePoint 2010 environments:

On any server that hosts SQL Server, it is very important that the server achieve the fastest response possible from the I/O subsystem. More and faster disks or arrays provide sufficient I/O operations per second (IOPS) while maintaining low latency and queuing on all disks.

SharePoint 2010 provides new control to render the Lists - XsltListViewWebPart, that replaces previous controls, such as ListForm, ListView, DataFormViewPart

SharePoint 2010 releases in variety of type, editions and licence versions. There are

SharePoint 2010 ships with 3 new master pages additionally to the default.master page

SharePoint 2007 provides the out-of-the-box (OOTB) approval workflow, but unfortunately this workflow doesn't work with groups.

SharePoint 2010 provides the better performance for the List, however some limitations still have place: Maximum number of List Items is 50 million Constrains that block Lists: Max of 8kb of data per list item (not including attachments) Max of six projected fields allowed on joins

Never use the IQueryable<T>.Where extension method when querying ListItem objects.

Using the Windows Server with the Domain Controller role was always not a good idea, due to the performance issue having the hard drive cache turned off.

The SPUtility.HandleAccessDenied method provides the functionality to redirect users to the standard "Access Denied Page" pragmatically, thus asking them to re-logon. One of the scenarios of such usage is the public sites, where access to the standard SharePoint specific pages still exists and you want to block those pages (source)

Unlike crawling SharePoint sites on SharePoint Server 2010 or SharePoint Foundation 2010 the crawler cannot automatically crawl all subsites in a site collection from previous versions of SharePoint Products and Technologies. Therefore, when crawling SharePoint sites from previous versions, you must specify the URL of each top-level site and each subsite that you want to crawl.

Developing SharePoint applications that use browser-enabled InfoPath forms requires a lot of interactions with the Web Services and it's usually done via DataSources properties of the InfoPath. You store all your connections to the Web Service into the DataSources and uses properties name to communicate.

Sometimes you might be in the situation when you accidentally deleted your SharePoint site from IIS. It's not a disaster, because nothing happened to your site, except you lost the access.

Using SharePoint 2007 on Windows Server 2008 might bring additional steps to configuration that didn't exist in Windows Server 2003. On of the most questioned area is "why I can't save Office Document to the SharePoint Library"?

Question:
>> Our company uses GMail for corporate mail. How can we configure the SharePoint to work with @gmail mailbox?

As you know SharePoint 2010 provides you "sandboxed solutions" to run your code in the restricted environment (for testing or other purposes) that doesn't affect the production farm functionality.

The Stsadm command-line tool of SharePoint 2007 has the following limitations: As part of a farm backup, backs up, but cannot be used to restore the configuration database or Central Administration content database. For more information, see Recovering the configuration database and Central Administration content database. Site collection backups affect performance, and they can cause access errors. They should only be used when the site collection is locked. Site collection backups can be slow when working with collections larger than 15 GB. We recommend that you use database backups if you are working with site collections larger than 15 GB. Note:  
If you want to individually back up a site collection that is larger than 15 GB, we recommend that you move it to its own database, and then use a database backup. Source

Question:
>> Hello, I'm using InfoPath with dozen of DataSources that query data from Web Services, lists and etc. I'd like to know how can I update DataSource URL at run-time and use URL from config?

SharePoint 2010 provides you rich JavaScript functionality extending the client model. New functionality comes with the SP.js that locates in 14(Hive)\TEMPLATE\LAYOUTS\SP.js

 SharePoint Server 2010 adds a default OrderBy clause to SPQuery call that orders the result set by content type, which ensures that folders are returned before list items.

SPQuery object of SharePoint 2010 can fail or block results if we don't limit the result set.

SharePoint 2010 doesn't allow you to install the "Complete" mode on non-domain local user accounts by default, because it's considered as "Development" environment and you should install in "Single Server" mode.

Question:
>> How can I convert List Template to a Feature

SharePoint 2010 removes Site Directory template, and you can't create it anymore (almost), but for the compatibility reasons the migrated sites will show the Site Directory.

When you try to print the SharePoint 2010 page you will find that site header and navigation is printed with you content. Very often you don't need that service information and would like to see the page content only.  This can be easily done via the custom CSS  that turns off the unnecessary elements from the printing.