That's a rather generalist statement. I played it with my girlfirend, my bestfriend and room mate and his girlfriend and we didn't really enjoy it that much. Just wasn't enough variety apart from "shoot the bullet sponge with a different coloured weapon". If Borderlands took the Serious Sam/Pain Killer route of instead of fighting the same enemies with tweaked health, have a wide variety of enemies that come in massive hordes so it actually felt like you and your weapons were getting more powerful it would've been a better game.
The world also felt way too flat. Boring grind missions more that would've been more welcomed in a MMORPG. The weapons, for all the developers talked about, didn't feel different from each other. Slightly changed stats isn't a choice to me, it's just pointless busy work.
The classes had balancing issues which basically came down to "if you're not playing the Siren you're doing it wrong". Vehicles seemed like a last minute addition and for the most part were actually more dangerous to ride in than going on foot.
tl;dr. Borderlands was an aRPG almost exactly like Diablo with a changed perceptive and a slightly shallower experience (if that's possible). If you enjoy that genre than you'll enjoy it. If you're anything like me you'll just find it grindy without any well substance to keep you going, the type of game you look back and ask: "why did I spend 6 hours playing this game?".