Try replacing an upper left O2 sensor or a right rear shock absorber on a 98-02 Crown Vic and get back to me on that "if it isn't simple they designed it wrong" thing. Shocks and oxygen sensors are a maintenance item, usually replaced every 30-50k. They should be designed for easy replacement, right? Surrrrrrre they are. 
p
I'll repeat: If it takes an hour per cell they designed it wrong. It's a battery, not a shock, and replacing the O2 sensor on my saturn was a 5 minute job, mostly looking for the right wrench.
If the battery packs are rated for 150k miles, I can almost guarantee the extended service interval will result serviceability coming in a distant second to design. Count on working in, around, and through a LOT of irrelevant stuff when servicing those "easily replaceable" packs. That will become especially true if hybrids become truly mainstream and are forced to be economically competitive in the open market.
They're already on the market. The battery pack is heavy, fairly large, and decoupled from the engine. It only needs a pair of wires(heavy gauge to be sure, but still wires) to the controller. Right now they're placing them in the trunk/under the back seat.
Bad analogy. In most applications plugs require the removal of a simple dust shield to access them, if that much. Plugs are also stand-alone items accessable as a single mechanical element without the need for further dissasembly or removel of accessories, parts, and body panels. Battery packs may be located in the trunk or under the seat, but you still have to do more than pop off a dust shield to access them. Plus, you don't have to worry about plug wires welding themselves to the body should you accidently let one of them drop. Then there's the potential for future battery technologies to be a single sealed unit (a lot of potential, in fact, as economy standards force the adoption of smaller, lighter vehicles).
Well, your listing examples where you need to dissassemble the engine to get to them is just as bad of an analogy. I DID factor in an hour or so to get the battery in/out after all. Plugs should be a ten minute job for a monkey wrench that's paying attention. Most of those batteries have shutoffs for safety already.
As for making the batteries sealed units, well, it depends on how likely they are to have to service them during the warranty period...
What I hear from local hybrid owners tends to contradict that. Though they do get slightly better economy with their hybrid, it isn't the "Oh My God look at this!!" that some marketing would have you believe. Two people in my office bought hybrids. Neither would buy them again if given the option of an equivalent gas or diesel powered vehicle.
They're easy to get to stats. I'm sure the cab companies, that are running a number of hybrids, could get you actual mileage statistics. Besides, don't regular vehicles also tend to use more fuel than EPA estimates?
The argument I can see in favour of the hybrid as a city car is pollution displacement. Overall the level of pollution emitted may be similar, but the hybrid is not chucking out pollutants in such significant amounts in population centres. It's not necessarily a good argument, but then I am reminded of the level of pollution build up on the Duomo in Florence.
Good point.
I'll be perfectly honest: On average, yes, a hybrid at this point is a status symbol. I just wanted to point out that in the right circumstances it can actually make sense.
Oh, and the next gen 'pluggable' hybrids should do even better - going from NiMH to LiIon has a number of advantages. While LiIon and the various related chemistries are more expensive, LiIon is half the weight for the energy, and has almost twice the charging efficiency - NiMH is around 66%, LiIon is 99% efficient. 50% more power returned for what you put in is a big deal, and can give you a lot of miles over time.
