Generally speaking, so long as you buy some sort of name brand memory, it will work fine as long as you are not running it outside specs (overclocking). If you are going to push memory beyond what it is rated for, then quality and manufacturer begin to matter more.
I have always used Samsung SDRAM when possible. I have had good experiences overclocking with it. On the other hand, I have also had very good experiences overclocking Micron. A few years ago, I had a pair of 32MB Samsung original dimms with -G10 memory on them. They were rated for 66MHz CAS2 operation. They easily ran 100MHz CAS2. I gave those to a friend, because 64MB just wasn't enough memory. I now run a pair of generic 128MB dimms, with Micron -8E chips on them, rated for 100MHz CAS2 operation. They easily run 133. For what it is worth, I also got a bunch of PNY 100MHZ CAS2 rated 32MB modules with -8 Siemens chips for free after rebate that ran 133 just fine too. The overclockability is a function of not only the chips, but also the modules. Samsung modules are very good quality. I got lucky with my generic modules with Micron chips, but buying generic modules is a little risky if you are overclocking. PNY modules also appear to be well manufactured, and the ones that I got were overclockable. As for chips, I have had good luck with Micron, Samsung, Siemens, and LGS (Lucky Goldstar) chips. I have had bad luck with Hyundai, NEC and Toshiba chips. Of course, overclockability will vary from batch to batch with any brand.
Nack