Don't worry about silverlight...seriously...I've never installed silverlight on any of my browsers and it's fine. What the heck uses a stupid microsoft proprietary framework that's impossible to work with? No one, which is why Microsoft have now withdrawn support for it.
Flash, well...yeah so HTML5 use is growing for webpages (so elegant!) and now some applications are being made in HTML5 (I'm even making some games in it atm
)but Flash is still predominant across the web, however, not having Flash wont stop you browsing, there's nearly always a mobile version or simple HTML version of every site you visit and you'll be redirected automatically. You'll not be able to play online flash games but then you probably wouldn't bother on an ipad anyway.
Tablet wise, you just need to decide if you're Android or iOS. Wouldn't recommend going for a tablet which isn't one of these. If you own any other Apple product then you should probably go for the ipad as you'll carry over most of your aps, if you're not then go into a store and check out an Android tab and see if you like it.
I'm an Apple person, I work with Android tabs and phones at work, and I just think the OS is really clunky, I can't be bothered to deal with it at home. I like all the auto synching that iCloud just takes care of for you.
I want to browse itunes, click on an ap, buy it and then it syncs to my ipad via icloud automatically so I can play it in seconds, if anything happens to my ipad or iphone and I get a new one I can get my entire phone or ipad data back in about 2 minutes, which is important to me.
The thing is, I suspect iOS is so intuitive to me because I've been using it for 6-7 years on various macs and iphone/ipads are just the same really. Also because my main computer is a MBP it works with all my Apple devices really easily, so you may want to take my apple love with a pinch of salt, signing in with my apple ID anywhere (phone/ipad/work mac/home mac) and getting all my shiz is amaze to me but might be useless to others.