I would like to hear from SharePoint experts who have experience in both SharePoint 2007 and SharePoint 2010 to share with the community on what are some of the great (or good) features that SharePoint 2007 has but however SharePoint 2010 does not have it.
Not sure there would be too many. Usually, if a feature is 'good', it is left in the product for the next release. Features that don't work well or those 'not so good' features will be generally improved upon for the next release.
An example would be the service application architecture in 2010 as an improvement over shared services in 2007, or Business Connectivity Services in 2010 as an improvement over the Business Data Catalog in 2007.
In addition, I'd say Microsoft generally try to make versions backwards compatible with each other as much as possible, so unless there are significant changes in architecture such as the examples above, they will try to avoid removing functionality just for the sake of it.
The way SharePoint handles different authentication methods.
In SharePoint 2007 you could extent a web application and set up FBA in one zone and Windows authentication in the other zone, and you had different URLs to access each type of authentication. This obviously wasn't the best solution but it worked.
In SharePoint 2010 you can now have both FBA and Windows authentication in the same zone (woohoo!) except the catch is you end users have to select which authentication type they wish to use before logging in and this is not user friendly at all (boohoo!).
I thought, OK - I'll extend the web app just like I did in 2007! This works, except unless you turn on FBA in your Windows Auth zone and Windows Auth in your FBA zone the users can't see each other at all (in 2007 this worked fine) and the problem with this is the point I mentioned above - the login screen is just awful.
In the FBA zone I was able to point it to the default FBA login screen as a "custom" screen but it wasn't so easy in 2010. I had to write a custom login page that redirected the users to the windows auth login url. This seemed work but as time goes on we have been finding problems with it. For example, our search account could no longer authenticate on that zone and as such wouldn't crawl it.
Needless to say, this has been a pain for me to support. A feature that Microsoft supposedly improved upon shouldn't be this much of a hassle.
Outside of this one thing, I pretty much find 2010 amazing compared to 2007.
One thing I miss from 2007 is the My Links functionality. It's possible to "enable" it with some changes, but they replaced it for Tagging and Notes. Not exactly the same thing.
Otherwise, i have't missed anything else in 2010