Will I see performance benefits from an SSD in my laptop?

I have a Dell Latitude D520 1.6ghz, 4gb ram. I'm looking to postpone a laptop upgrade by getting one of the new Intel X25-M G2 SSDs.

Any thoughts or experiences on if such an upgrade will help? I know these things kill in benchmarks but on a laptop, I'm concerned there are other bottlenecks I'd quickly run into (for all I know, this lappy's sata controller--if it has one--can't push bits quickly enough for SSD to matter).

You will most absolutely and definitely and positively see an improvement. Laptop hard drives are usually the #1 bottleneck in a system. My Dell Latitude D420 came with a 4200RPM drive. Choke. Cough. Slow. Your D520 probably isn't as bad out of the box, but its drive is still likely an I/O bottleneck.

I installed an OCZ Vertex 250GB SSD in my other laptop, a Macbook, some time back, and it flew compared to the original 5400RPM drive.

These new SSDs are amazing compared to hard drives. But don't go cheap -- some SSDs can be slow. The OCZ Vertex I purchased is a good product, and so is the Intel you're referring to ... it would have been my other choice.

An SSD will provide a very notable performance improvement, particularly in boot times and application load times thanks to their amazingly fast random read performance.

The best information I've seen on the subject is from Anandtech. You can see it here:

http://www.anandtech.com/storage/showdoc.aspx?i=3531

You most likely will see an improvement. As you mentioned there are other bottlenecks, but the SSD will reduce latency to at least some degree. You may want to watch your power usage though, as SSDs tend to chew more power, which is an issue for laptops.