Many good points here... Alkaline batteries these days are cheap. There is no reason to panic about buying throw away batteries, especially if you buy them in bulk as stated many time before.
For those of us who have been conditioned from birth to abhor using throw away batteries, I feel rechargeables help us to sleep at night. There is also a certain satisfaction from reusing a battery. That has to be taken into account. There are probably hundreds of different approaches to replacing the 9v and 'D' cells with rechargeables. You can go with rechargeable 'packs' or drop in rechargeable replacements for the said stock battery. I prefer packs, it allows more flexability (obsess-ability?) I just juiced my 30v 3300mah NMH pack, and it took about 10min to charge. My 'AA' rechargeables that I use for the heaters take much longer, but I have 2 sets. If I could, I would like my whole system to run off of batteries!
Eric
Emotiva XPA-2, Magnepan MMG (mod), Quickie (mod), JRiver, Wyrd4sound uLink, Schiit Gungnir, JPS Digital power cord, MIT power cord, JPS Labs ultraconductor wire throughout, HSU sub. powered by Crown.