That all depends on how much data you're dealing with in individual QlikView applications. Developers need to be able to either load the entire application (or sometimes a portion of the data for the application) on their own PC. In our shop, I believe all but three applications are small enough to fit on a 32-bit PC with 2GB of RAM. The largest requires a 64 bit machine with 8 GB of RAM. In our shop, only ONE development PC has the larger configuration, and we remote control that PC as necessary. Since there are so few apps that require that PC, and since I ended up as the point of contact for all three, we've had no problems with more than one developer needing the machine at once that couldn't be resolved with some simple communication.
As a rough estimate for memory required for an application, divide the size of the raw data by 10, then add 5-10% for each concurrent user. So let's say your'e making a sales application, and you have 100 GB of sales data that you want to display, and you expect to have 20 concurrent users. That's going to take probably 10 GB of RAM on the development machine, and 20-30 GB of RAM on the server. But let's say that's 10 years worth of sales data. The developer in this case can likely limit the load during development to only a single year, and the application will only take 1 GB of data, and he or she will be able to do the work on a 32-bit machine with 2 GB of RAM. But even in this case, you may want at least ONE 64-bit development machine with 10+ GB in order to test the complete load.
Monitor size seems like a non-issue to me. We develop for the LOWEST resolution in common use at our company (1024 x 768). So if the developer's monitor is at least that lowest resolution, there's no problem. It is, of course, easier to work on a large monitor in many cases. But I'm personally running a single 1280 x 1024 monitor, oriented vertically, and it's perfectly sufficient for QlikView development.
