I alway go via the share menu to upload my clips and let FCPX do everything. It pretty much does the same thing - exports the project first, then uploads it. If you go into the FCP Projects folder on your render disc, you'll find a 'Shared' folder, which contains the exported video. Hence if the upload failed for any reason, your internet got disconnect for example, you can just reupload the exported file from the shared folder rather then re-rendering the whole thing again.[DOUBLEPOST=1369996780,1369996646][/DOUBLEPOST]
Rendering is CPU intensive. It'll use the CPU mainly and will be slower if you are doing other tasks on the computer at the same time. Hence while rendering, as Andrew suggested, best to leave the system to do its job so it can use the CPU at full capacity if it needs to.
Having more RAM is god for use while you edit and create the project.