playing against higher rated players

It all depends. The ideal opponent is probably someone slightly higher rated than you (100-200+). This is the next level you want to get to so it's useful to see what they are doing better than you. Also you have a chance to beat them so this keeps motivation up. Getting whupped over and over by someone much higher rated is less likely to be beneficial because they are several levels above you. Either way, if you review your games and strive to understand what happened in each game it will be useful.

Playing a really high level will be about as informative as playing the computer on max level: not helpful at all, really.  You get destroyed and will have no clue why, most likely.   I know when I face off against 2000+ (rare, but tournaments etc can do it) I often have no clue what they did to me without computer assistance afterwards (which I can do against the robot too).  But playing people a little bit better than you... is great.  You can understand what they did, why you lost, most of the time.  

Yeah. One of the reasons for improving against stronger players upto +200 is that you will understand why you lost and what to change or improve. You will also lose against +500 but may not know why and if you do, that sort of improvement may be out of your immediate reach. To bigger step.