SQL Server Mirroring vs 3rd party replication products such as DoubleTake
SQL Server's native database mirroring includes something really slick: automatic page repair.  If the principle detects a corrupt page on disk, it fetches a clean copy of the page from the mirror automatically without taking the database down.  You don't get that level of database repair with any third party product.  That database awareness is one of the reasons I prefer the native tools - well, that and I just don't trust third party filter drivers on database servers.  I've seen too many blue screens of death due to third party filter driver bugs.

Bad news: database mirroring is deprecated in SQL 2012.  This means it's still around for this version, but will be removed in the future.

Fantastic news: SQL Server 2012 introduced AlwaysOn Availability Groups to replace mirroring, and they're awesome.  You can actually query or back up from the mirror, and you get up to four mirrors.  Some can be synch and some can be asynch.  This gives you all kinds of flexibility over database mirroring, and it blows away the third party tools.