While this may not be the forum to put this in...I will chime in as well
ANY virtual world requires maint., server restarts and will always encounter some sort of downtime. In the grand scheme of things SL is not that expensive, a paltry monthly fee (I pay much more for other virtual worlds/games), and if you pay quarterly it's like getting one month almost free.
Now down time. I have not experienced much down time in SL. The land I own is extremely low lag, and it is "rebaked" or restarted pretty regularly to keep it fresh. I have many breedables on my land, and a night club that supports all the particles you can wear. So maint is important to keeping things running smoothly. But, I do know many have had issues, this is a virtual world and much like real life, will experience hiccups. I have in other worlds experienced entire days of server downtime due to maint.
Cost, well we all have the ability to control our costs here. Downtime has not affected my ability to pay my tier. Overall soft sales have at times made it close, as I try to not purchase linden to pay my tier. Real life economy will also effect the virtual economy. So blaming LL for costs is like blaming the cable company. If you can't afford it, don't get it
Are there other virtual worlds out there? Sure there are, but you have to make the choice to give up the already established grid here, and start over somewhere else.