we own 4 bumgenius and 2 fuzzibunz diapers. i did not buy any of them; they were gifted to us at my husband's diaper party and at christmas. we LOVE them. they work very well, and i love that you can adjust the absorbency with more or fewer inserts. (i like the bumgenius ones better because they are easier to adjust size-wise and the inserts are easier to put in. fuzzibunz inside is very rubbery and the inserts are tough to slide in.)
if you wanted to cloth diaper using only bumgenius, it would probably run you about $400. this would get you about 24 diapers (i have seen several websites that advertise a "buy 4, get one free" deal) and that would last about two days for a newborn, and 3 or 4 days for an older baby or a toddler. because i have never bought disposables, i don't know exactly how much they cost, but it depends on how often you change your baby, too. i'll estimate about $70 for one month (sourcesource) which averages out to about $840 per year ... or you could put that money towards cloth. just 6 months of what you would pay for disposables would buy you all the bumgenius you'll need for one baby .. and perhaps more! if you take care of your diapers they can last for more than one child. and that's for top-of-the-line diapers!!
we use our pocket diapers at night because they are more absorbent than our prefolds. to make our prefolds more absorbent and to help wick the moisture away from my daughter's skin, i purchased a yard of fleece ($8 at walmart), cut it into strips and sewed it on her prefolds. so, for 18 prefold diapers, we paid about $42, a little more than the cost of just 2 bumgenius pockets.
we also have 3 diaper covers that we rotate between (two econobum and one thirsties duo wrap). i think i like the thirsties cover better because it has leg gussets that help keep moisture in. my daughter has skinny little legs right now, so before they get chunkier the leg gussets are wonderful. the price (around $12 each) is great for these too.
all of the diapers we own (and probably all the diapers i will ever buy) are one-size. this means they are adjustable and fit baby from birth to potty-training. the only problem with this is that they look HUGE on my 10lb daughter. they don't feel huge or fall off or anything -- there's just a lot of fabric there, and i know as she keeps getting bigger the diaper will look smaller and smaller.