I have been developing with LINQ to SQL for about six months now on my website www.myfitnessjournal.com I use Linq to Sql for the DAL and have had no real issues at all. It has been great to work with although there were some tricks to things like transactions and updating data using WCF services but when I tried EF at the beginning of the project I found that there were some pretty important things missing that I needed, also I was using SQL server for the database so Linq to Sql was great for that. If I remember correctly some of the Date methods and String comparisons weren't completely supported yet in EF. Of course all I hear lately is that EF will eventually replace L2S but if you wait for that you can be certain some other mystery project will be almost ready to replace EF. So in other words I just used the tool that worked better for me. All of these things have a decent learning curve but if you learn L2S you won't have any problem moving to EF later.
Nick Lecrenski Founder/Lead Developer http://www.myfitnessjournal.com