Best .NET memory and performance profiler?

No. I have tried pretty much every .NET profiler on the market (ANTS, vTune, OptimizeIt, DevPartner, YourKit), and in my opinion dotTrace is the best of the lot. It is one of only two profilers I have used (the other being YourKit) that has low enough overhead to handle a highly CPU-intensive application.

If and only if your application is relatively light, I could recommend ANTS Profiler. Its line-by-line stats are sometimes quite useful, but they come at a price in profiling efficiency.

For memory profiling you have both the free CLR profiler and the commercial .NET memory profiler. Both are excellent but the latter is a bit more polished.

We've got on really well with AQTime. The great thing from our point of view is that it does the unmanaged parts of our code too.

It hasn't been mentioned yet, but for memory analysis Windbg is about as thorough and low-level as you can get. Using it in combination with sos.dll is incredibly powerful, but there is a fairly steep learning curve.

It's a free tool though, and Tess Ferrandez' blog is a great place to start with it. ANTS and other profilers are much more user-friendly, but Windbg can slice and dice the managed heap like none other in my opinion.

Ants Profiler just released version 4.
We use it, and are quite happy with it. There's a 14 day trial to evaluate (as is true for most offerings).

We use DotTrace like you, but in the past we used Ants Profiler by RedGate. It is a nice tool also.

I am very happy with RedGate ANTS. The only other one I tried was the one that comes with Visual Studio Team, and it sucks.

nProf is a good tool if you're looking for something free. It's kind of finicky at points, and a little buggy, but if you're on a tight budget, it'll do the job.