Spelunky is difficult to win, sure, but I wouldn't say it's "punishing". Unless you're an advanced player tediously farming each level for cash to get some ridiculous score, a full playthrough takes well under an hour (meaning you'll have lost little, time-wise, with any given death). There are even shortcuts you can unlock that let you start in later areas of the game (though, counter-intuitively, you'll usually have a better chance of success when starting from the beginning, so the shortcuts are mostly good for practicing moving around, surviving, and experimenting in later areas of the game).
(Unlocking the final shortcut, though...that can be a bit punishing. ;D )

Also, most deaths, at least in hindsight, should be predictable. I'd say no more than 10-20% of deaths are "bullshit" deaths stemming from the procedural generation of the levels & placement of enemies screwing you; the rest will be player error -- whether that means failure to plan ahead, inattentiveness to your surroundings (e.g., because of rushing too much), pressing the wrong button (or the right button at the wrong time), or just generally going somewhere you should've avoided (excessive greed kills in this game).