SQL 2008 VS. SQL 2005

Arguably the most potent tool for DBA's in 2008 would be Policy Based Management. Tom LaRock did a nice 3-video walk-through with Brent Ozar which you should probably check out:

http://tomlarock.com/?s=policy+based+management

I also cover PBM in my blog/talks/presentations

http://sqlchicken.com/category/policy-based-management/

My PBM fanboy-ism aside, here's the list to all the new features available in SQL 2008

http://www.microsoft.com/sqlserver/2008/en/us/whats-new.aspx

I did a post recently on features in SQL 2008 that you can take advantage of without having to change your applications. It's at http://msmvps.com/blogs/robfarley/archive/2009/12/18/high-roi-items-for-sql-server-2008.aspx

I think some of the best features in SQL2008 is Date datatype (no more conversions to strip the time), Data compression (requires less IO operations) and filtered indexes.

I activated PAGE compression in one of our databases and reduced the size from about 1 Tb to 400Gb and increased the performance due to less IO. Data compression uses more CPU, but we are using a server with 4 quad processors and 64Gb memory. :)

With filtered indexes i can create more covering indexes with increased read performance with only slight write overhead. Covering indexes reduces Key lookups.

My company has found that the most useful new function is spatial data. We deal with location information all the time, and being able to query directly against the data is a huge advantage.

The enhancements to SSMS2008 over SSMS2005 are fairly significant, I especially like adding missing index information to execution plans and the addition of intellisense. The ability to query multiple servers at once is very useful in some limited situations. http://www.sqlservercentral.com/articles/Management+Studio/63536/ provides an introduction to some of the SSMS enhancements.

Also, small tweaks to TSQL such as the ability to initialize a variable when it is declared are nice in a readability sense.