I havent played the old metroid games, and I've only played a small bit of the DS castelvania games.
Nostalgia seems to play a role in how well liked this game is.
Will I like it?

Not to sound rude, but why don't you download the free trial that comes with all arcade games, and then see whether or not you enjoy it.....

Have you tried the demo?

I gots burned by Trials HD, liked the demo, then it got crazy hard, im down half of my investment.
I'll try it but its not the almighty arbiter of truth I used to think it was.

yeah I wont like it then :p 
I'll have to give the ol credit card another battering then