I have been using the Oracle SQL Developer (because it's free) and at first hated every minute spent with it. I am still having weird problems with graphics, as it's running on Vista and there seems to be some sort of graphics driver problem (luckily, no-one can get it to run properly on Vista, so I am not alone in this), which makes its use quite cumbersome.
Nevertheless I had to learn how to cope with it and now I must admit it's a neat and very useful tool (NOT ONLY) for querying an Oracle database. I suppose you could query other DBs from it as well, for instance I have used it to query some legacy MS Access DBs, and so I believe you could query SQL Server as well.
You can do data migrations, imports/exports, see OWA output, and allegedly also DEBUG (step through, set breakpoints, etc...) PL/SQL code, but I haven't tried this. I have been fine with sqlplus command-line so far :) Do give it a try, and don't let the Vista-related graphics problems give you a wrong impression :)
