well i use the rk launcher which eats about 3mb extra memory wid the default icons. other than that no performance degradation coz flyakite is a shell pack (ie it replaces some system files).
you can use yzdock or object dock which consume less memory. but the advantage wid rk launcher is that it supports docklets for both these docks! possibilites are endless...you can script ur own sysstats docklets and they are really cool. check this screenie out:
*img215.imageshack.us/img215/4539/macdesktop5ev.th.jpg
it shows a clock, whose second hand is active (not visible in pic!), a cpu monitor, a network monitor, laptop battery monitor etc. wid all this rk launcher takes about 10mb of ram and 3% cpu usage in my case. but if u do away wid active docklets (which update every few secs) the cpu usage becomes zero and the ram requirement really drops!
ps: version 0.4 beta of rk launcher has been a bit buggy wid sysstats. 0.3 has been perfectly stable for me!