IntelliJ IDEA 4.0 is out. You can get 30 days full-featured evaluation version , and I already have a license I got with discount during new year promotion ($250 for personal license).
Once you have it, compare it, memory usage wise and performance wise, with your favorite Eclipse version, be it M7 or not. I bet that IDEA will be snappier - that is based on my experience with IBM WebSphere Application Developer 5.1, which is the memory hog.