Digging this thread up from dormancy...
There is one disadvantage of slow chargers, especially trickle chargers (which often require more than 24 hours to fully charge most NiMH batteries): If you use them as the sole means of recharging NiMH batteries, larger crystals will form on the battery electrodes, making the charging less efficient and less complete. Don't be surprised that what seems to be 'fully charged' using a slow charger alone is nowhere near as full as you think! (Like, an 1850mAh NiMH battery that's reaaaally sloooooow-charged will not perform any better or last any longer between charges than an earlier-generation 1400mAh NiMH battery that's been quick-charged in a 'smart' charger.) And extremely slow-recharging is actually damaging to the usable life of the NiMH batteries, by not allowing the batteries to become anywhere near fully charged - because more and more large crystals continue to form on those electrodes. In fact, I have had 700mAh NiCd batteries that have always been charged in such a trickle charger (one that delivered only 45mA of current even to AA batteries); it took all of 22 hours to 'fully' charge those NiCds, and the capacity dropped from 700mAh when new to only 450mAh after only 25 charge cycles! (And yes, I always have discharged those NiCds completely before recharging.) As a result, I'd recommend those trickle chargers only for topping off already charged NiMH batteries.
My RatShack 23-422 charger has been giving me good service - but it's very inconvenient for me to use, because I have often-used portable devices that use one AA battery or three AAA batteries - and I have to charge all three batteries as soon as they get discharged. But my charger only allows charging batteries in pairs (2, 4, 6 or 8 at a time) - and worse, all of the batteries to be charged in the 23-422 charger must be of exactly the same size, exactly the same capacity, and exactly the same chemical formula (which means that if I were to charge 1800mAh NiMH AAs in my RatShack charger, all of the other batteries being charged at the same time must all be 1800mAh NiMH AAs, as well). That will guarantee unevenly-charged sets of batteries.
So, this past Monday I ordered a Maha charger from Thomas Distributing (it's the successor model to the still-available C204F, the C401FS). The new C401FS has both negative-pulse charging and delta-slope termination (like a good smart charger should), eliminating the need for a separate discharge/conditioning cycle (helpful when charging partially discharged NiMH batteries - NiCd's still need full discharging for best results). Second, unlike the 204F (which still requires the batteries to be recharged in pairs), the 401FS can charge one to four AA or AAA batteries at a time - and with a separate charging circuit for each cell (unlike the one-hour chargers from Energizer and Ray-O-Vac, which actually use only one or two commonly shared charging circuits for all four cells). Third, the 401FS offers a choice of two charging modes: 'Fast' (which claims to charge 1700mAh AA NiMH batteries in 1 hour 40 minutes), and 'Slow' (which claims to take 5 hours for the same-capacity NiMH AAs). The charging current in 'Fast' mode is 1000mA for AA, 500mA for AAA; in 'Slow' mode, 300mA.
The charger is being shipped as I type my post here, and it's being shipped from downstate Illinois (yep, the same state that I live in). So, I'd expect it to arrive on either Friday of this week or Monday of next week. And yes, I will use the 'slow' mode most of the time, unless I need the fully-charged set of batteries in a hurry.