<p>Recent conversations with colleagues have produced varying points of view on this matter. What say you, SO members?</p>

<p>I know, even the concept of scalability can be taken in so many different ways and contexts, but that was part of the discussion when this came up. Everyone seemed to have a different take on what scalability really means. I'm curious to see the varying takes here as well. In fact, I posted a <a href="https://stackoverflow.com/questions/214246/what-does-scalability-mean-to-you">question</a> just for that concept.</p>

It greatly depends on which LINQ provider you are using and how you are using it. LINQ probably is not know for amazing execution speed but is rather provides developers with substantially better productivity.
According to
this
link even with some of the CTPs Linq to SQL was already better than using direct SQL in some cases.
If you are concerned with Speed and are using LINQ to objects alot
here
is a codeplex project (I think) for a provider that can give you 1000x performance improvements.