Sorry about that. I only read the first post thoroughly, then I just randomly scrolled and have read somewherer about iMaca and love getting something something, so I just concluded you're getting one. Anyway. Get a SSD (your computer will be reborn, I promise you that) and 4GB RAM (more, if it fits in your laptop). Lightroom 4 has this stupid bug, which won't flush memory. After editing about 20-25 pictures, all my RAM is used up and even if I restart Lightroom, it won't help much, other than restarting whole computer.
Have a look on the App Store for free Memory Flushers. They work a treat.
I hate to be that guy, but: No. No no no no no.
Memory flushers are often detrimental to overall system performance. Here's why: Unused RAM is wasted RAM. It's money better spent on something else. Therefore, when you quit an application or an application frees/flushes memory, Mac OS X won't actually free it. Instead, the system keeps the data in RAM around in case it's needed again later. For example, if you reboot your Mac and launch Photoshop, it'll take quite a long time to launch. If you quit Photoshop and launch it again a second time, it'll load *much* faster. This is because the system kept the data around in RAM so it didn't have to load Photoshop from disk the second time.
This cached information is freed from RAM automatically if something else needs it. Using "RAM flushers" deletes this cache, meaning you lose the performance benefits it provides.
You can read more about this from Apple themselves here
(under the "Inactive" header).
Basically, if you have more than 0Mb of free RAM on a Mac OS X machine at the end of the work day, that RAM was a waste of money and you should've spent it on something else.
Source: I'm a programmer by trade — it'd my job to know this boring crap like the back of my hand.Edit:
Sorry, forgot the useful part of this post: The simple way to tell if your computer needs more RAM is to look at the "Page Outs" figure in Activity Monitor. Page Outs happen when the system has run out of RAM to store everything it needs, so it starts purging stuff out to disk. Doing that is super slow (even with SSDs) and you should avoid it if you can. For example, my Mac has 16Gb of RAM and its uptime is nearly 80 days (I just sleep it rather than shutting it down). In this time, page outs total around 200Mb, which is perfectly fine. My free memory figure is never more than 1Gb or so, and all my apps load super fast because they're in the cache. However, because the page outs figure is so low, adding more RAM won't really increase performance.