Many macbook problems - it is leopard or my hardware or both?

Well, in a nutshell:

I had the cracking palmrest problem with my 1st Gen 1.83 CD Macbook, sent it in for repair and since then the problems seem to be stacking up. First of all, the start time is SLOW. I mean, I turn on the computer and get a grey screen for about 2 mins before the apple on the grey screen even appears. Log in itself is so slow I can usually make a cup of tea while it's doing its thing - so basically log in takes about 5 mins. Once up and running, it seems to be fine except that certain operations get long beachballs, such as getting the system profiler to come up or starting up itunes. It also freezes up occasionally. Now, I've just discovered that my optical drive is, as far as my computer is concerned NOT THERE!!

I did install leopard (upgrade install) a few weeks before I sent the computer in. While I found it a bit buggy, it's just a nightmare right now.

I've zapped pram, fsck'ed it (it's clear), repaired permissions, and done a mem test. Is there anything else I can do? Do you think the repair people did a job on my computer? I'm getting a bit annoyed with the problems on this machine. If I have to send it in, it will be the THIRD time within a year.