The SqlServer driver uses INFORMATION_SCHEMA schemas whenever possible. Though in SqlServer 2000 (every service pack) there is a confirmed bug in at least one INFORMATION_SCHEMA view which makes them unusable if you want to retrieve meta information for schemas other than dbo, hence system tables are used instead in that case.
It's unlikely Microsoft has changed the system tables dramatically, but in case they have, it will give an error, though there are no errors of that kind reported thus far.
SqlServer 2005 isn't official supported yet. One possible problem which can arise is when you create tables with UDT's. The SqlServer driver now assumes UDT's are always resolvable to native SqlServer types. Other than that, it should be ok.
SqlServer 2005 will get its own driver later this year. The SqlServer DQE and templates should run fine on Sqlserver 2005