Outpost 09 Free on the R50 (spec below) has given me no problems at all. To save time I simply resorted to choosing auto learn mode every time, and everything seemed to fall into place without a worry. I've borrowed it out a couple of times, the kids were on it (both under 10 years old) and a couple of their programs on it when returned but no problems. I rang up a few times as the household are relatively computer illiterate, kids aside, and everyone was quite at home with the setup. Bit of a surprise really.
Tho' came back with MSE had turned itself off. Turned back on and updated so all good.
I also have OA on a couple of computers, which I like a lot but I find OA a bit more work intensive.
Edit - I should add that the kids programs are loaded to the computer from disk, and then link to the internet site where they password in to their online accounts. They then find more than enough to keep them occupied. The mum is computer literate, so she has always bought the disks - like ScoobyDoo, SpongeBob, etc (they dont cost that much really) - and ensured the young ones are aware that safe practice is taking place.