General :: Ubuntu NR - Install Vs Live-persistent

I have an old EeePC 701 4G netbook that I'm about to reconfigure for a friend who needs it to read PDF files, surf the net occasionally and do few other things. I'm going to install Ubuntu Netbook Remix, version 10.4.

Now, the 701 only has four gigabytes of internal storage, and I'm unwilling to spend money on it to expand its memory. When installed UNR takes up about 2.3 gigabytes, which leaves a bit more than a gig available for user data, and that's not much at all.

However, I could copy the live files off the memory stick in the main drive and use the remaining space for a casper-rw partition. Then it'd be only a matter of editing the bootloader in order to have a system that saves changes. This way I could fit the system on only 700 megabytes.

My question is: is there any drawback to running a persistent live off the main drive as the operating system? Something that would make me prefer eating up two thirds of the drive with the system, rather than just a fifth of it?

I imagine upgrades would eventually take up a lot of space, as they'd essentially copy a lot of the system in the live partition, but this is easily solvable by not performing them. I don't think the intended user would miss them, since she'll only really need three or four apps.