Got this recently (Last week, Tuesday maybe) and I was fairly disappointed with the lack of insanely big bosses. There's like, 3? And none of them are particularly difficult (maybe they are on the 2nd time around). Hell Bone-head is pretty much the only enemy I fear (when I have to do the quest).
took some beating at first as well, but only because I was like 5 levels lower than him
I enjoy it though, just wish it was longer and had bigger bosses. I completed it just over a day (Fully - All quests), going through my 2nd playthrough to reach level 40 and 50 and I'm going to get the DLCs when I get a new debit card. Hopefully they'll be worth it.
The game is glitchy as hell though. I joined one of my friends games and within about 20 seconds he'd given me a shield that when I clicked it in my inventory it gave me +31095(guess, number is around that) money and an increase to my shield (not sure how much per click), so my level 2 character couldn't be killed in the Dahl Headlands on the second playthough (I think my shield once I'd got up to "$9999999" was around the 550,000 mark.)* He's also got a bunch of weapons that some level 50 duplicated for him, jus' cos. One of them kills everything at his level in one shot. And the other kills everything. Ever. It's a shotgun that fires rockets, 5000x10 damage per shot.
Oh it's got a +1000% burst rate on it. So he just rains hell on everything.
It's rather ridiculous to be honest.
*Note: I didn't glitch on my main save (Siren - level 37), it was a secondary save - it takes all the fun out of the game glitching.