I have just recently purchased a rhythm reel by ross reels. I have not had the chance to use the reel yet, but, it balances very well with my 5wt rod. As far as the plastic drag knob goes...I am not to concerned about it breaking. It may not even be plastic! It could be made from derlin which is used for a lot of reel handle. This is something you could ask Ross Reels.
I have an old scientific anglers reel( same as a hardy marquis)25+ yrs old, it has a plastic drag knob and hub cover. although the reel does look quite used, these plastic components still look like new.If you do have a problem, ross reels come with a lifetime warranty.
I am very happy with the quality of the rhythm and sure you will be happy aswell if you choose a ross reel.

[This message has been edited by Northern Fisher (edited 14 April 2005).]