Well, that depends on card price and importance of write speed. I am happy with transcend 4gb 150x. It was cheaper even than Transcend 4GB SDHC class 2 and write speed is excellent and much better than the class 2 card (and even slightly better than class 6 card), see also test here.
http://www.hjreggel.net/cardspeed/sp...cards-sdh.html

Write speed can be measured either by copying some big video over USB which is practical test where it really matters or by doing synthetic test via dd i.e. something like
then just divide size (80 MB?) by the result in seconds

True that some SD cards may be of poor quality with pathetic write speed but fast sd cards are faster when writing then SDHC class 2 and may be cheaper since SDHC is still novelty and sell in lower volumes. Well at least this was true at the time I bought my card. When checking same shop today I see Transcend SDHC class 2 price dropped to be now lower than the 150x one (by approx $8, 4GB SD 150x ~= $58, 4GB class2 SDHC ~= $50) so this may not apply anymore.

When you are planning use cards for storing video and expect to write often to it, fast writes are important. In normal usage writing is not so frequent and read speed of all current cards is similar and good enough.