As a PHP / MySQL developer using .NET and SQL Server, I've moved over to WinHost.com from ReliableSite.net.  It's a really solid option for those looking to get the most out of their providers, but be forewarned: there are some things you'll need to get your hands dirty with that you may not be used to (like setting up sub domains via IIS).

Overall, though, for $5 a month, I think having PHP5, a MySQL 5 database, .NET 4 support, as well as a SQL Server 2008 database, is definitely worth the price of admission.

Now my blog is hosted on my own domain, and I've got enough options to make sure that I can explore whatever development paths I desire.