It is a known fact that our phone has a very hard time managing its memory. But, lucky for us, there is a solution.
Not sure if I can define zram but from what I understand it is noticeably better. Also, try messing around with your vm heap via the vm heap tool from the market (have to be rooted) I've found that keeping mine above 47, as suggested by another user, tends to keep things in check and running smooth. I'm currently running mine at 80 with Autokiller Memory Optimizer set on optimum and have had amazing results. What setup are you running right now? I know its says PWGB but what kernel, what I/o scheduler, governor, etc...
That link will take you to Comradsven's TKSGB Kernel forum. I would suggest reading all the way through, if possible, from page 40 where the link will take you to the end of the zram, akmo, vm heap, etc... discussion.
As far as I know, and anyone feel free to correct me on this, zram is a feature enabled in custom kernels. I have yet to mess with it but I'm sure I will sooner rather than later. So it would not be compatible with stock kernels. Either way, to get the most out of your fascinate you should pop a new kernel in there. Lagfix will greatly increase the capabilities of you phone and in some cases will allow you to control your voltages, I/O schedulers, Governors, and even Color/Gamma tweaks for your screen.
I have personally had the most luck with the kernel I linked above. I'm using the Bleedingedge version of it as I like having more manual controls over the colors, gamma, and rgb multipliers our phones beautiful super amoled screen has to offer. I currently have it OC'd at 200-1200 mhz (States: 1200 at -50 mv, 1000 at -50, 800 at -75, 400 at -75, 200 at -75) with CFQ and Smartass v2, a vm heap size of 80, AKMO set to optimum (as well as all the fun advanced tweaks, depending on what settings your kernel is on. Havn't had good luck with the network tweaks in those though), and I ran the Adrenaline Shot XIX speed tweaks script. My phones flies at this point and I have had no hot reboots or locking up. I should also note that I am running TSM Resurrection 1.2 as it seems to agree with my phone nicely. For some reason didn't have much luck with Pool Party, though I loved that rom to death.
I also had an amazing experience with Imoseyons Lean kernel but I opted out as I wanted more of the manual control of things. Amazing kernel but very very low in extras.
Bottom line is this:
Our phones are very capable devices, they just need tweaking. Each handset is unique and will react differently to different roms, kernels and tweaks. Try and experiment with some rom/kernel combos and see what works out for you.