I pretty much try to do all maintenance myself.
First off, it's cheaper than taking it to the shop (unless you really screw it up).
Second, it's fulfilling to do these things yourself. Not to mention fun.
Third, it's interesting. You get to know more about the machine you ride and appreciate it more. I also feel you're more "in tune" with the bike and are able to figure out when somethings wrong faster. Which I think is more important with a bike than with a car.
As for intervals, I usually stick to what my Haynes manual prescribes. If I can do it myself I'll try to do it. For example oil changes, changing filters, lubricating various parts, checking/replacing spark plugs. These are all fairly easy jobs to do and don't really take much time or really special (or expensive) tools.
However, I don't have a workshop -I have to work on the street- nor do I have a means of lifting the bike, other than my paddock stands. As such I cannot disassemble the front forks (which require special tooling anyway) or stearing head etc.
When the time comes I might try to change the chain & sprockets myself. It might take a while but I recon it shouldn't be all that difficult. I'd also like to replace the clutch if (when) that should become necessary, but I gather this job requires a specialist tool which can only be found through a Honda Dealer.
At the moment I'm working my way through the 12.000km maintenance interval for my Hornet (. I wanted to change the oil/filter today, but when I set everything up I noticed that the filter on the bike didn't have a nut on top to unscrew it, unlike the new K&N filter I bought. So I'll have to go get an oil filter wrench tomorrow to get it off. Instead I decided to check the spark plugs which were -to put it mildly- a bit harder to get to than the CBR125 I owned before.
But I got the job done and after everything was plugged back in it ran on all 4 cylinders, so I guess that was a success.