I don't know much about Samsung drives, never used one, but I think it would be wise to pick up a better rep hard disk for primary use, and since this is your backup drive, go for it if its cheap, let us know how it performs.
 
For me, Maxtor and Western Digital never gave me a problem.
Seagate is ok, but hard to find.
IBM are fast but expensive, I don't know much about stability.
I hate Fujitsu.

Samsung drives are kinda crap they are ok if your looking for a cheap crap drive that will probably die in the future 6-8mos.

As for myself: IBM is n°1, then Maxtor and Western Digital. Samsung's drive are cheap and very low at work, just the same for Seagate (though they're doing High Level drives). And 5400 is really low ! Why hesitate for an ata133 ?

Why hesitate for ATA133? Simple: because it's useless in performance gains. By today's standards, even ATA66 has to be fully utilised.
 
Burst transfer speeds, yea, ok...but sustained read/writes do not top 30-40 MB/s (IDE).

Yup. If ATA drives can get up to 10k rpm, we could see a transfer rate above this, but I'm not positive.

I don't have an ata133 controller, so buying a ata133 drive is kinda useless right now. I bought myself a seagate 40GB 5400 RPM and frankly, i can't see a difference in speed with my 30GB maxtor 7200 rpm.
In my oppinion HD's are a question of luck. People who haven't had a single problem say it's good, others who had a broken one say it's crap... My maxtor crapped out on me within a week...I had to RMA it "great". I'll see how things go with the samsung. For now i'm pretty happy with it.

I benchmarked my maxtor ata100 30GB 7200 RPM and my samsung ata100 40GB 5400 RPM both on a pci ata100 promise controller using sisoft sandra:
 
maxtor score: 15932 (=performance below ata66)
samsung score: 20916 (= performance between ata66 and ata100)
 
How come the maxtor is so slow???