I honestly think it's subjective. Most people have not noticed any slow down with the upgrade.
If there had been the internet would be a fire storm by now with fanbois and anti-apple partisans slugging it out. Remember the fuss over antennagate.
That said your slow browsing may not be due to the iPad. There's line noise, contention ratios and bandwith all having an effect. Also the release was apparently delayed while Apple tried to improve the iPads connectivity, so if you genuinely are having problems in this area do check out the forums for help.
I'd just ignore the multitasking as this should have no effect on the pads performance. Theres no need to close the apps listed in the background. If your main app needs the ram the iPad will release it from the older one's automatically.